Community herbal monograph on
Thymus vulgaris
L.,
Thymus zygis
Loefl. ex L., aetheroleum
To be specified for the individual finished product.
Well-established use
Traditional use
With regard to the registration application of
Article 16d(1) of Directive 2001/83/EC as
amended
Thymus vulgaris
L. or
Thymus zygis
Loefl. ex L. or
a mixture of both species, aetheroleum (thyme
oil)
i) Herbal substance
Not applicable.
ii) Herbal preparations
Essential oil.
Well-established use
Traditional use
In liquid dosage forms for oral use (indication 1)
and in liquid or semi-solid dosage forms for
cutaneous use and use as a bath additive
(indication 2).
The pharmaceutical form should be described by
the European Pharmacopoeia full standard term.
1 The material complies with the Ph. Eur. monograph (ref.: 01/2008:1374).
2 The declaration of the active substance(s) for an individual finished product should be in accordance with relevant herbal
quality guidance.
Community herbal monograph on
Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
EMA/HMPC/131901/2009
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4.1.
Therapeutic indications
Well-established use
Traditional use
Indication 1)
Traditional herbal medicinal product used as an
expectorant in cough associated with cold.
Indication 2)
Traditional herbal medicinal product for the relief
of symptoms in coughs and colds.
The product is a traditional herbal medicinal
product for use in specified indications exclusively
based upon long-standing use.
4.2.
Posology and method of administration
Well-established use
Traditional use
Posology
Indication 1)
Adults and elderly
Oral use: 4-5 drops (single dose), 3-5 times daily.
The oral use in children and adolescents under 18
years of age is not recommended (see 4.4 Special
warnings and precaution for use).
Indication 2)
Adults and elderly
Cutaneous use: in liquid and semi-solid dosage
forms in concentrations up to 10%; apply up to 3
times daily.
Use as bath additive: 0.007 – 0.025 g per litre.
Adolescents
Use as bath additive: 0.007 – 0.025 g per litre.
Children 6-12 years
Use as bath additive: 0.0035 – 0.017 g per litre.
Children 3-6 years
Use as bath additive: 0.0017 – 0.0082 g per litre.
One bath every day or every second day.
The cutaneous use in children and adolescents
Community herbal monograph on
Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
EMA/HMPC/131901/2009
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under 18 years of age is not recommended (see
4.4 Special warnings and precaution for use).
The use as bath additive in children under 3 years
of age is not recommended (see 4.4 Special
warnings and precaution for use).
Duration of use
Indication 2)
Duration of a bath: 10-20 minutes.
Indications 1) and 2)
If the symptoms persist longer than 1 week, a
doctor or a qualified health care practitioner should
be consulted.
Method of administration
Indication 1)
Oral use.
Indication 2)
Cutaneous use: apply on the chest and the back.
Use as bath additive: recommended temperature
of bath: 35 – 38 °C.
4.3.
Contraindications
Well-established use
Traditional use
Hypersensitivity to the active substance.
Use as bath additive:
Full baths are contraindicated in cases of open
wounds, large skin injuries, acute skin diseases,
high fever, severe infections, severe circulatory
disturbances and cardiac insufficiency.
4.4.
Special warnings and precautions for use
Well-established use
Traditional use
Indication 1)
Like other essential oils Thyme oil should not be
applied to the face particularly in the nasal area of
babies and infants under the age of two years
because of the risk of a laryngospasm.
When dyspnoea, fever or purulent sputum occurs,
a doctor or a qualified health care practitioner
Community herbal monograph on
Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
EMA/HMPC/131901/2009
Page 4/7
should be consulted.
The use in children and adolescents under 18
years of age is not recommended due to lack of
adequate data.
Indication 2)
Use as bath additive:
When dyspnoea, fever or purulent sputum occurs,
a doctor or a qualified health care practitioner
should be consulted.
The use in children under 3 years of age is not
recommended because medical advice should be
sought and due to lack of adequate data.
In cases of hypertension, a full bath should be
used with caution.
Cutaneous use:
Like other essential oils Thyme oil should not be
applied to the face particularly in the nasal area of
babies and infants under the age of two years
because of the risk of a laryngospasm.
When dyspnoea, fever or purulent sputum occurs,
a doctor or a qualified health care practitioner
should be consulted.
The use in children and adolescents under 18
years of age is not recommended due to lack of
adequate data.
4.5.
Interactions with other medicinal products and other forms of
interaction
Well-established use
Traditional use
None reported.
4.6.
Pregnancy and lactation
Well-established use
Traditional use
Safety during pregnancy and lactation has not
been established.
In the absence of sufficient data, the use during
pregnancy and lactation is not recommended.
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Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
EMA/HMPC/131901/2009
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4.7.
Effects on ability to drive and use machines
Well-established use
Traditional use
No studies on the effect on the ability to drive and
use machines have been performed.
4.8.
Undesirable effects
Well-established use
Traditional use
Indication 1)
Hypersensitivity reactions have been observed.
The frequency is not known.
Indication 2)
Hypersensitivity reactions and skin irritation have
been observed. The frequency is not known.
If other adverse reactions not mentioned above
occur, a doctor or a qualified health care
practitioner should be consulted.
Well-established use
Traditional use
No case of overdose has been reported.
5.1.
Pharmacodynamic properties
Well-established use
Traditional use
Not required as per Article 16c(1)(a)(iii) of
Directive 2001/83/EC as amended.
5.2.
Pharmacokinetic properties
Well-established use
Traditional use
Not required as per Article 16c(1)(a)(iii) of
Directive 2001/83/EC as amended.
5.3.
Preclinical safety data
Well-established use
Traditional use
Not required as per Article 16c(1)(a)(iii) of
Directive 2001/83/EC as amended, unless
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Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
EMA/HMPC/131901/2009
Page 6/7
necessary for the safe use of the product.
Thyme essential oil had no mutagenic or DNA-
damaging activity in either the Ames test (strains
TA1535, TA1537, TA98, TA100, with and without
metabolic activation) or Bacillus subtilis rec-Assay.
Adequate tests on reproductive toxicity and
carcinogenicity have not been performed.
Well-established use
Traditional use
Not applicable.
16 September 2010
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Thymus vulgaris
L., Thymus
zygis Loefl.
ex L.,
aetheroleum
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Assessment Report
Table of contents
Table of contents
................................................................................................................... 2
1. Introduction....................................................................................................................... 4
2. Historical data on medicinal use ........................................................................................ 6
2.1. Information on period of medicinal use in the Community ........................................
6
preparations and indications.......................................................................................
8
3. Non-Clinical Data ............................................................................................................... 9
preparation(s) and relevant constituents thereof ...........................................................
9
3.1.1. Assessor’s overall conclusions on pharmacology................................................. 1
3
preparation(s) and relevant constituents thereof ......................................................... 1
3
3.2.1. Assessor’s overall conclusions on pharmacokinetics ............................................ 1
3
preparation(s) and constituents thereof ..................................................................... 1
3
3.3.1. Assessor’s overall conclusions on toxicology ...................................................... 1
5
4. Clinical Data ..................................................................................................................... 15
4.1. Clinical Pharmacology ....................................................................................... 1
5
including data on relevant constituents ...................................................................... 1
5
including data on relevant constituents ...................................................................... 1
5
4.2. Clinical Efficacy ................................................................................................ 1
6
4.2.1. Dose response studies.................................................................................... 1
6
4.2.2. Clinical studies (case studies and clinical trials).................................................. 1
6
4.2.3. Clinical studies in special populations (e.g. elderly and children)........................... 1
6
4.3. Overall conclusions on clinical pharmacology and efficacy ...................................... 1
6
5. Clinical Safety/Pharmacovigilance................................................................................... 16
5.1. Overview of toxicological/safety data from clinical trials in humans.......................... 1
6
5.2. Patient exposure .............................................................................................. 1
6
5.3. Adverse events ................................................................................................ 1
6
5.4. Serious adverse events and deaths..................................................................... 1
7
5.5. Laboratory findings .......................................................................................... 1
7
5.6. Safety in special populations and situations ......................................................... 1
7
5.7. Intrinsic (including elderly and children) /extrinsic factors ...................................... 1
7
5.8. Drug interactions ............................................................................................. 1
8
5.9. Use in pregnancy and lactation........................................................................... 1
8
5.10. Overdose ...................................................................................................... 1
8
5.11. Drug abuse.................................................................................................... 1
8
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
EMA/HMPC/131903/2009
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5.14. Overall conclusions on clinical safety ................................................................. 1
9
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L.,
Thymus zygis
Loefl. ex. L., aetheroleum
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1.
Introduction
1.1.
Description of the herbal substance(s), herbal preparation(s) or
combinations thereof
Herbal substance(s)
Not applicable.
Herbal preparation(s)
Thyme essential oil (= thyme oil).
Definition
Essential oil obtained by steam distillation from the fresh flowering aerial parts of
Thymus vulgaris
L.,
T. zygis
Loefl. ex. L. or a mixture of both species (Pharm. Eur. monograph 01/2008:1374).
T. zygis
Loefl. ex. L. not in IPNI, only
T. zygis
L.
Pharm. Eur. monograph on Thymi herba:
T. zygis
L.
Appearance
Clear, yellow or very dark reddish-brown, mobile liquid with characteristic, aromatic, spicy odour,
reminiscent of thymol (Ph. Eur.).
Commercially the crude thyme oil is called “red thyme oil” because of its deep colour. After
redestillation “white thyme oil”, a light yellow oil, which smells similarly but sweeter and less pungent
is obtained (Böhme et al
.
2008).
Composition:
Essential oil: there are at least 6 chemotypes of
Thymus vulgaris
(Thompson et al.
2003) with different
compositions of the essential oil; only the ‘thymol’-type with thymol as predominant compound
complies with the definition in the European Pharmacopoeia. The dried herbal substance contains up to
2.5% essential oil; the main components are thymol, carvacrol, p-cymene,
-terpinene, linalool,
-
myrcene, terpinen-4-ol. Some compounds occur partly as glycosides (e.g. p-cymene-9-ol (Takeuchi et
al. 2004, Kitajima et al. 2004, Stahl 1991).
Composition according to Pharm. Eur.:
β-Myrcene: 1.0 per cent to 3.0 per cent,
γ-Terpinene: 5.0 per cent to 10.0 per cent,
p-Cymene: 15.0 per cent to 28.0 per cent,
Linalol: 4.0 per cent to 6.5 per cent,
Terpinen-4-ol: 0.2 per cent to 2.5 per cent,
Thymol: 36.0 per cent to 55.0 per cent,
Carvacrol: 1.0 per cent to 4.0 per cent.
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
EMA/HMPC/131903/2009
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CH
3
CH
3
CH
3
CH
3
CH
3
OH
CH
3
OH
OH
CH
2
OH
H
3
C CH
3
H
3
C CH
3
H
3
C CH
3
H
3
C CH
3
H
3
C CH
3
H
3
C CH
3
Thymol
Carvacrol
p-Cymene γ
-
Terpinen Linalool
ß-Myrcene
1.2.
Information about products on the market in the Member States
Regulatory status overview
Member State
Regulatory Status
Comments (not
mandatory field)
Austria
MA
TRAD
Other TRAD
Other Specify: Combinations only
Belgium
MA
TRAD
Other TRAD
Other Specify: Combinations only
Bulgaria
MA
TRAD
Other TRAD
Other Specify:
Cyprus
MA
TRAD
Other TRAD
Other Specify:
Czech Republic
MA
TRAD
Other TRAD
Other Specify: Combinations only
Denmark
MA
TRAD
Other TRAD
Other Specify: Combinations only
Estonia
MA
TRAD
Other TRAD
Other Specify: Combination only
Finland
MA
TRAD
Other TRAD
Other Specify:
France
MA
TRAD
Other TRAD
Other Specify:
Germany
MA
TRAD
Other TRAD
Other Specify:
Greece
MA
TRAD
Other TRAD
Other Specify:
Hungary
MA
TRAD
Other TRAD
Other Specify:
Iceland
MA
TRAD
Other TRAD
Other Specify:
Ireland
MA
TRAD
Other TRAD
Other Specify: No products
Italy
MA
TRAD
Other TRAD
Other Specify: Combination only
Latvia
MA
TRAD
Other TRAD
Other Specify:
Liechtenstein
MA
TRAD
Other TRAD
Other Specify:
Lithuania
MA
TRAD
Other TRAD
Other Specify:
Luxemburg
MA
TRAD
Other TRAD
Other Specify:
Malta
MA
TRAD
Other TRAD
Other Specify:
The Netherlands
MA
TRAD
Other TRAD
Other Specify: No products
Norway
MA
TRAD
Other TRAD
Other Specify:
Poland
MA
TRAD
Other TRAD
Other Specify: No products
Portugal
MA
TRAD
Other TRAD
Other Specify:
Romania
MA
TRAD
Other TRAD
Other Specify:
Slovak Republic
MA
TRAD
Other TRAD
Other Specify: Combination only
Slovenia
MA
TRAD
Other TRAD
Other Specify:
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
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Spain
MA
TRAD
Other TRAD
Other Specify: No products
Sweden
MA
TRAD
Other TRAD
Other Specify: No products
United Kingdom
MA
TRAD
Other TRAD
Other Specify:
MA: Marketing Authorisation
TRAD: Traditional Use Registration
Other TRAD: Other national Traditional systems of registration
Other: If known, it should be specified or otherwise add ’Not Known’
This regulatory overview is not legally binding and does not necessarily reflect the legal status of the
products in the MSs concerned.
2.
Historical data on medicinal use
2.1.
Information on period of medicinal use in the Community
Evidence of the period of traditional use:
The medicinal use of thyme oil is documented at least since 1589 (Dispensatorium Noricum, cited in
Gildemeister et al.
1961). The essential oil of
Thymus vulgaris
is published in pharmacopoeias and
standard text books of phytotherapy since many decades (e.g. British Pharmaceutical Compendium
1949, Tschirch 1917, Stahl 1962, Martindale 1972).
In Germany products containing thyme oil as the only active ingredient are on the market at least
since 1976. Therefore, for thyme essential oil, a period of at least 30 years in medical use, as required
by Directive 2004/24 EC for qualification as a traditional herbal medicinal product, is fulfilled.
The medicinal use of thyme oil in the specified indications is a European tradition.
Evidence regarding the indication in traditional use:
Oral use:
Catarrh of the upper
respiratory tract, bronchial
catarrh, symptoms of
bronchitis, cough with
spasms
Martindale 1972, Böhme et al.
2008, Leung 1980
Posology:
Oral use: 4 - 5 drops (for example
on a piece of sugar or in honey) 3-
5 x daily (Hager CD-ROM 2008).
Czech Pharmacopoeia (Český
lékopis, 2007): single dose for oral
use - 0.1 g
Anthelmintic
Tschirch 1917, Stahl 1962
no posology available
Oromucosal use:
antiseptic mouthwash,
tooth pastes
Gildemeister et al. 1961
no data on the strength available;
a concentration of 0.005% thymol
is proposed (equivalent to 0.009 –
0.014% essential oil) Haffner et al.
(1984)
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
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Cutaneous use:
Pruritus associated with
dermatoses
German commission B (thyme oil as
bath additive)
Leung 1980
for bath additives see below
Bruises, sprains
Leung 1980
no posology available
Supportive treatment of
acute and chronic diseases
of the airways
German commission B (thyme oil as
bath additive)
Leung 1980
for bath additives see below; in
unctions in a strength of 10%
Rubefacient, counter-
irritation
Martindale 1972, Stahl 1962
no posology available
Inhalation:
Supportive treatment of
acute and chronic diseases
of the airways
German commission B (thyme oil as
bath additive)
see below
Madaus 1938: only reference to the use of thymol, not of the essential oil.
Stahl-Biskup E et al
.
in Wichtl (2009): only reference to thyme herb or thymol, not to thyme oil.
Authorized products containing thyme essential oil as the only active ingredient with
evidence of tradition:
Germany:
Several bath additives are on the market at least since 1976.
Concentration of thyme oil in bath additives: 5 – 15%.
Posology of thyme oil:
Adolescents, adults: 0.7 – 2.5 g / 100 l water (= 0.007% - 0.025%)
Children 6-12 years: 0.35 – 1.68 g / 100 l water (= 0.0035% - 0.0168%)
Children 2-6 years: 0.175 – 0.82 g / 100 l water (= 0.00175% - 0.0082%)
Children 6 months – 2 years: 0.7 g / 100 l (= 0.007%)
Once daily or 3-4 times weekly
Water temperature: 35-38°C
Duration of a single bath: 10-20 minutes
Indication: for the relief of symptoms in coughs associated with cold with viscous mucilage.
Plausibility of the effects and critical discussion of traditional indications:
Cough and cold, oral use:
The expectorant activity of thyme herb is attributed to the content of essential oil. The efficacy of
thyme oil is plausible when administered orally.
Cough and cold, cutaneous use, bath additive:
It is commonly accepted in literature (e.g. Hänsel & Sticher 2007) that essential oils are absorbed
through the skin because of their lipophilic nature. After cutaneous administration and during a bath
containing thyme oil the constituents evaporate from the vehicle. Thyme oil will be inhaled and
absorbed via the lung additionally. It is therefore plausible that thyme oil applied to the skin in semi-
solid dosage forms or used as a bath additive will act in coughs and colds similar to the oral
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
EMA/HMPC/131903/2009
Page 7/19
application. Expectorants may be interpreted for oral use by the layman. Therefore a different wording
for the indication for cutaneous use and use as a bath additive is proposed.
Antiseptic gargle:
The use as an antiseptic gargle or mouthwash is plausible due to the antibiotic activity of the essential
oil. However, there is very limited evidence of an actual traditional use in this indication. Clinical
experience (see chapter 4.2) is based on products containing synthetic antiseptic agents too. Therefore
this indication will not be proposed.
Bruises, sprains:
Cutaneous application results in an increased blood flow in the skin, an effect which is often used
traditionally for the supportive treatment of bruises and sprains. However, for thyme oil there was only
a very recent reference citing this indication. There is no evidence for a traditional use in this
indication.
Pruritus:
The indication ‘pruritus associated with dermatoses’ is mentioned in the respective monograph of the
German commission B. However, this indication does not seem to be plausible according to the data
from pharmacological experiments. Therefore this indication will not be proposed for traditional herbal
medicinal products.
Anthelmintic:
The use as anthelmintic agent is obsolete.
2.2.
Specified strength/posology/route of administration/duration of use
for relevant preparations and indications
Proposals for indications for traditional use:
Different indications are proposed depending on the route of administration:
Oral use:
Traditional herbal medicinal product used as an expectorant in cough associated with cold.
Cutaneous use, use as bath additive:
Traditional herbal medicinal product for the relief of symptoms in coughs and colds.
Further indications found in literature are not supported by traditional use or by a traditional posology.
Posology:
Oral use: 4 - 5 drops (for example on a piece of sugar or in honey) 3 - 5 x daily (Hager CD-ROM
2008). 1 drop = app. 0.05 ml = app. 0.045 g.
Dosage recommended in the last version of the Czech Pharmacopoeia (Český lékopis 2007): single
dose for oral use - 0.1 g (= app. 2-3 drops).
At least 0.004 g essential oil per litre for preparation of a full bath (= app. 1 drop per litre = 120 drops
per full bath = app. 0.5 g) (German Commission B).
In ointments in concentrations up to 10% (Hager CD-ROM 2008).
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L.,
Thymus zygis
Loefl. ex. L., aetheroleum
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Use in children and adolescents:
The only available data come from the authorized products in Germany (see above) and from
confidential data provided from the German Authorities. See chapter 5.6.
Duration of use:
Duration of a bath: 10-20 minutes.
Although thyme oil is considered as safe the duration of use should be limited to 1 week, otherwise a
doctor or a qualified health care practitioner should be consulted.
3.
Non-Clinical Data
3.1.
Overview of available pharmacological data regarding the herbal
substance(s), herbal preparation(s) and relevant constituents thereof
Antibacterial activity
The essential oil exerts a strong antibacterial activity on Gram-positive and Gram-negative bacteria.
The activity is mainly attributed to thymol and carvacrol (numerous articles published, e.g., Simeon de
Buochberg et al. 1976, Janssen et al. 1986, Menghini et al. 1987, Patakova et al. 1974, Allegrini et al.
1972, Janssen 1989, Farag et al. 1986, Lens-Lisbonne et al. 1987, Vampa et al. 1988, Chalchat et al.
1991, Dorman et al. 2000, Hersch-Martinez et al. 2005).
Oils with higher percentage of phenolic compounds show higher inhibitory activity (Penalver et al.
2005). Correlations between concentrations of thymol and MIC and minimal bactericidal concentration
suggest that the formation of membrane perforations is the principal mode of action of thymol against
oral bacteria (Shapiro et al. 1995).
Thyme essential oil had the lowest minimum inhibitory concentration (0.03% V/V) against
Escherichia
coli
and
Candida
among 20 essential oils tested (Hammer et al
.
1999).
The antibacterial activity of 14 essential oils and their major components was evaluated by agar-plate
dilution assay under sealed conditions, with agar used as a stabilizer for homogeneous dispersion by
Inouye et al. (2001). Of the selected strains of four major bacteria causing respiratory tract infection,
Haemophilus influenzae
was most susceptible to the essential oils, followed by
Streptococcus
pneumoniae
and
Streptococcus pyogenes
.
Staphylococcus aureus
was less susceptible. No cross-
resistance was observed between penicillin-sensitive and penicillin-resistant
S. pneumoniae
.
Escherichia coli
, used as a control bacterium, showed the lowest susceptibility. Essential oils
containing aldehyde or phenol as a major component showed the highest antibacterial activity,
followed by the essential oils containing terpene alcohols.
Antifungal activity
The essential oil is highly antifungal, when tested on fungi and yeasts, e.g.
Candida albicans
. This
activity is mainly attributed to phenol compounds thymol and carvacrol. Thymol interferes with the
formation and viability of hyphae and induces morphological alterations in the envelope of
Candida
albicans
(Braga et al. 2007, 2007a).
Thyme oil inhibits the mycelial growth of
Aspergillus flavus
and
A. niger
(Paster et al. 1990) and at
concentrations of <= 500 ppm completely inhibits dose-dependently fungal growth and mycotoxin
production of
Aspergillus flavus
,
A. parasiticus
,
A. ochraceus
and
Fusarium moniliforme
(Soliman &
Badeaa 2002).
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L.,
Thymus zygis
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The therapeutic efficacy of a 1% solution of thyme oil and thymol against
Trichophyton
mentagrophytes
,
T. rubrum
and
T. tonsurans
was examined on 2-months old Wistar rats. During the
37-day observation period the oil - treated rats were cured (Sokovic et al. 2008). In dilution assays
thyme oil showed much higher antifungal potency than the commercial fungizide bifonazole (Sokovic et
al. 2009).
Thyme oil was antagonistic by vapour contact against an experimental tinea pedis in guinea pigs
infected with
Trichophyton mentagrophytes
. Thyme oil killed the conidia, inhibited germination and
hyphal elongation at concentrations of 1-4 µg/mL air (Inouye et al. 2001a).
Inouye et al. (2007) investigated in vitro the ability to treat tinea pedis with a combination of essential
oils, heat and salt in a foot bath.
Agar blocks implanted with
Trichophyton mentagrophytes
were immersed in 0.1% aqueous agar
containing two-fold dilutions of essential oils with or without sodium chloride at 27
O
C, 37
O
C and 42
O
C
for 10 and 20 min. The fungicidal activity of essential oils was markedly enhanced by treating at 42
O
C
for 20 min as compared with that at 27
O
C, showing 1/4 - 1/32-fold reduction of minimum fungicidal
concentration (MFC to kill 99.99%). Thyme essential oil rich in thymol showed a conspicuous activity.
MFCs were further reduced to 1/2 - 1/8 by the addition of 10% sodium chloride.
The in vitro activity of some essential oils (EO) (thyme red oil, fennel, clove, pine, sage, lemon balm
and lavender) against clinical and environmental fungal strains was investigated. The minimal
inhibitory concentrations were determined by a microdilution method in RPMI 1640 and by a vapour
contact assay. The inhibiting effects of EO in vapour phase were generally higher than those in liquid
state. According to both methods thyme red oil and clove were found to be the oils with the widest
spectrum of activity against all fungi tested (Tullio et al. 2007).
Spasmolytic activity
Thyme oil shows a spasmolytic effect on the smooth muscle and a contracture involving a direct action
on skeletal muscle by an unknown mechanism. The essential oils were diluted in methanol to give a
final bath concentration of 5x10
-5
and 2x10
-4
g/ml for rat diaphragm in vitro with muscle stimulated
directly or via phrenic nerve and 4x10
-6
-8x10
-5
g/ml for field-stimulated guinea-pig ileum studies (Lis-
Balchin et al. 1997).
Thymol has in vitro an agonistic effect on α1-, α2- and β-adrenoreceptors; the spasmolytic activity is
detectable in concentrations > 10
-6
M. In a concentration of 10
-4
M, thymol suppresses the
spontaneous contractile activity of the non striated muscles of the stomach of the guinea-pig. In higher
concentrations thymol exhibits a spasmolytic activity in the ratio of 1:10 compared to papaverine (Beer
et al. 2007).
Thyme oil inhibits the phasic contractions of the ileal myenteric plexus-longitudinal muscle preparation
of the guinea-pig. The ED
50
was found for thyme oil at 6.9 mg/L compared to papaverine which is 5
times more effective and isoprenalin (ED
50
0.0044). On the tracheal guinea-pig preparation papaverine
was 700-times more effective than thyme oil (Brandt 1988, Reiter & Brandt 1985).
Secretomotoric activity
Only historic reports are available from experiments on the secretomotoric activity.
Gordonoff (1931, 1932, and 1933) and Vollmer (1932) demonstrated secretomotoric and secretolytic
properties of thymol and thyme preparations.
A stimulation of the ciliary movement in the pharynx mucosa of frogs treated with diluted solutions of
thyme oil, thymol or carvacrol has been reported by Freytag (1933, cited in Hager CD-ROM 2008).
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Antioxidant activity
Antioxidative effects of thyme oil have been determined in various test systems in vitro (e.g., Youdim
et al. 1999a, Dorman et al. 2000, Kulisic et al. 2005, 2005a). Essential oils with high proportions of the
phenolic components thymol and/or carvacrol showed the highest antioxidant activities (Jukic et al.
2005, Chizzola et al. 2008). The antioxidant activity of p-cymene-2.3-diol, a minor component of the
essential oil, is considered as more potent than thymol or carvacrol which could be due to its dihydroxy
structure (Schwarz et al. 1996).
Thyme essential oil exhibited a dose-dependent protective effect on the copper-induced LDL oxidation.
The protective effect of essential oils is assigned to the presence of phenolic monoterpenes, thymol
and carvacrol, which are identified as the dominant compounds (Kulisic et al. 2007).
Youdim et al. (1999, 1999a, 2000, 2002) investigated the influence of thyme oil and of thymol on the
phospholipid polyunsaturated fatty acid composition, antioxidant enzyme activity and the phospholipid
fatty acid composition in several rat tissues. The rats were fed with a diet containing thyme oil or
thymol in an amount of 42.5 mg/kg BW/day. Beneficial effects could be found in different experimental
settings. Thymol alone was not more effective compared to the entire essential oil.
Anti-inflammatory activity
Thyme oil inhibits prostaglandin biosynthesis, thymol was less active in the COX-inhibition test
(Wagner et al
.
1986).
Thymol was shown to inhibit dose-dependently the experimentally induced release of neutrophil
elastase. The authors concluded that thymol may have a helpful effect in the control of inflammatory
processes present in many infections (Braga et al. 2006).
Further activities
Effects on the alimentary canal
In the stomach thymol (<0.5 mM) suppressed the generation of action potential and slow potential
changes without any marked change in membrane potential and membrane resistance. Increased
concentrations of thymol (>0.5 mM) reduced the membrane potential and membrane resistance. In
the ileum and rectum, thymol suppressed spike activity without any marked change in the membrane
potential. Although the membrane was completely depolarized, thymol (>1 mM) suppressed the
generation of phasic and tonic responses of the K-induced contracture evoked in the various regions of
the alimentary canal. Thymol (0.5 mM) suppressed spontaneous mechanical responses in the various
regions of the alimentary canal (Ito et al. 1974).
ACE-inhibition
Jukic et al. (2007) examined in vitro the inhibitory activity exerted by the main constituents of
essential oil obtained from
Thymus vulgaris
on acetylcholinesterase (AChE). The total essential oil and
selected compounds, specifically linalool and thymol, carvacrol and their derivatives thymoquinone and
thymohydroquinone, were tested for AChE inhibition. Thymohydroquinone exhibited the strongest
AChE inhibitory effect over the range of concentrations. The AChE inhibitory potential decreased in the
following order: thymohydroquinone > carvacrol > thymoquinone > essential oil > thymol > linalool.
Wound healing
After topical treatment of burned rats with thyme oil (1:1 diluted with olive oil) an increase in the
formation of new tissue could be observed (Dursun et al. 2003).
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Bone Metabolism
Thyme oil and thymol have been demonstrated to be efficient inhibitors of bone absorption in rats.
Thymol is a direct inhibitor in the osteoclast absorption pit assay (Mühlbauer et al. 2003).
Cardiovascular system
Thymol in concentrations of 1-10 mg/kg BW inhibited calcium channels in rats and lowered blood
pressure (Aftab et al. 1995).
Magyar et al. (2002) achieved a similar inhibition of calcium and potassium channels in canine and
human ventricular cardiomyocytes.
Szentandrassy et al. (2004) concluded from experiments on the Langendorff-perfused guinea pig heart
that the negative inotropic action of thymol can be explained by reduction in calcium content of the
sarcoplasmic reticulum due to the combination of the thymol-induced calcium release and inhibition of
the calcium pump. The calcium-sensitizer effect, observed at lower thymol concentrations, indicates
that thymol is likely to interact with the contractile machinery also.
Skeletal muscles
Thymol suppresses both Ca(2+) and K(+) currents in enzymatically isolated rat skeletal muscle fibers
in a concentration-dependent manner (Szentandrassy et al. 2003).
Thymol and carvacrol were able to evoke Ca(2+) release with EC(50) values of 158 +/- 16 and 211
+/- 55 µM respectively in heavy sarcoplasmatic reticulum vesicles isolated from skeletal muscle and
actively loaded with calcium (Sarkozi et al. 2007).
Effects on the CNS
Lim et al
.
(2005) investigated the stimulating or sedative effects of inhaling thyme essential oil by
using the forced swimming test (FST) with mice. The inhalation of thyme oil (p<0.05) resulted in
22.87% reduction of immobility. The same results were achieved when over-agitation was artificially
induced in the mice by an intraperitoneal injection of caffeine.
Mohammadi et al
.
(2001) investigated several phenol derivatives with regard to their ability to activate
directly the gamma-aminobutyric acid (GABA(A)) receptors in the absence of the natural agonist. This
mechanism is supposed to contribute to its sedative-hypnotic actions. Only compounds with the
phenolic hydroxyl attached directly to the benzene ring and with aliphatic substituents in ortho position
to the phenolic hydroxyl activated chloride currents in the absence of GABA. The concentrations
required for half-maximum effect were 200 µM for thymol, and 23 µM for the positive control propofol.
Insecticidal actions
Thyme oil is lethal against adult
Oryzaephilus surinamensis
,
Rhyzopertha dominica
and
Sitophilus
oryzae
(Shaaya et al. 1991).
Good insecticidal activity (>90%) against larvae of
Lycoriella ingenua
was achieved with thyme oil at
30 x 10
-3
mg/1 air. Carvacrol and thymol were effective at 10 x 10
-3
mg/l (Park et al. 2008). The LD50
against Tyrophagus putrescentiae, a stored food mite, is 10.2 µg/cm
2
in an impregnated fabric disk
assay (Jeong et al. 2008).
Mosquito control
Thymol and carvacrol are potent repellents in concentrations of about 0.05% in topical treatment (Choi
et al. 2002, Park et al. 2005).
Antihelmintic actions
Thyme oil in solutions of 1:2000 caused the death of ascarides in vitro. Non-phenolic constituents
demonstrated less activity (Akacic & Petricic 1956).
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Antiparasitic
Thyme oil is effective against
Trypanosoma cruzi
. Thymol may be the main component responsible for
the trypanocidal activity (Santoro et al. 2007).
In an in vitro growth inhibition assay with bloodstream forms of
Trypanosoma brucei
the ED50 of
thyme essential oil was found to be 0.4 µg/ml (Mikus et al. 2000).
Antiviral actions
The IC50 for thyme oil against herpes simplex virus type 2 was determined at 0.007% when the
essential oil was added at different stages during the viral infection cycle (Koch et al. 2008).
3.1.1.
Assessor’s overall conclusions on pharmacology
Numerous pharmacological activities are reported for thyme oil or for the isolated compound thymol.
Most experiments refer to the antimicrobial and to the antioxidant activity. These effects are primarily
used in food industry, where thyme oil is an effective agent against spoiling. The spasmolytic activity
and the few data on the secretomotoric activity make the use as expectorant in cough associated with
cold plausible.
3.2.
Overview of available pharmacokinetic data regarding the herbal
substance(s), herbal preparation(s) and relevant constituents thereof
No non-clinical data on pharmacokinetics are available.
3.2.1.
Assessor’s overall conclusions on pharmacokinetics
No non-clinical data on pharmacokinetics are available.
3.3.
Overview of available toxicological data regarding the herbal
substance(s)/herbal preparation(s) and constituents thereof
Acute toxicity
The LD50 of the essential oil p.o. in rats was 2.84 g/kg body weight (Von Skramlik 1959).
The intraperitoneal LD50 of thymus zygis oil in mice was 600 mg/kg body weight (Jimenez et al.
1993).
During antimicrobial activity assessment of high doses of thyme oil (0.05% compared to 0.01% and
0.06 mM diluted in ethanol) and thymol (24% content in thyme oil) simultaneously strong cytotoxic
effect on Caco-2 cells was stated (Fabian et al. 2006). The extent of damage in the cell population
caused by enteroinvasive
E. coli
was also widened. In accordance with this, the presence of the
evaluated substances at high concentrations in the digestive system could cause injury to intestinal
cells.
Subchronic toxicity:
In commonly used doses (up to 20 drops per day; as culinary herb) no acute or chronic toxicity is
reported for thyme oil (Mills & Bone 2000).
Chronic toxicity
No toxic effects were observed in rats after the addition of 1.0% of thymol to their diet for 19 weeks
(Hagan et al. 1967).
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Thymus zygis
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Mutagenicity and genotoxicity
Essential oil:
Thyme essential oil had no mutagenic or DNA-damaging activity in either the Ames test (strains
TA1535, TA1537, TA98, TA100, with and without metabolic activation) or
Bacillus subtilis
rec-Assay
(Zani et al. 1991). Although the Ames test lacked one of the currently used strains the negative result
could be regarded reliable, because the paper contains adequate description of findings and because
the Ames test is supplemented by the rec-assay.
Thymol and other constituents:
Thymol did not show mutagenicity in
Salmonella typhimurium
strains TA97, TA98 and TA100, with and
without S9 metabolic activation and 20 minutes standard preincubation time (Azizan et al. 1995).
Stammati et al. (1999) determined relative cytotoxicities of thymol and carvacrol and assessed their
potential genotoxicity in short-term assays. Both substances inhibited the colony-forming ability of
Hep-2 cells in dose-dependent manner. The results of an AMES-test in strains TA100 and TA98 were
ambiguous. Both substances were marginally more toxic to repair-deficient strain than to its repair-
proficient counterpart. The substances produced elevated revertant numbers in the strain TA100, but
not to a level generally considered significant. Effects in the SOS chromotest are interpreted as signs of
toxicity rather than real SOS induction. The authors conclude that the genotoxic potential of thymol
and carvacrol is very weak.
Concentrations of thymol and γ-terpinene above 0.1 mM significantly induced DNA damage in human
lymphocytes, however, below these concentration thymol and carvacrol significantly reduced the
oxidative DNA damage induced by H2O2 (Aydin et al
.
2005) or imidazolquinoline and mitomycin C
(Aydin et al. 2005a).
Thymol and carvacrol reduced the level of DNA-lesions caused by H2O2 in HepG2 and colonic Caco-2
cells (Horvathova et al. 2006).
Thymol in concentrations up to 520 μM did not increase the frequencies of chromosome aberrations in
Syrian hamster embryo cells compared to the control cells (Hikiba et al. 2005).
Azirak & Rencuzogullari (2008) investigated the in vivo genotoxic effects of carvacrol and thymol in
bone marrow cells of rats. Both carvacrol (10, 30, 50, and 70 mg/kg b.w. intraperitoneally) and thymol
(40, 60, 80, and 100 mg/kg b.w. intraperitoneally) significantly induced the structural and total
chromosome abnormalities (CA) in bone marrow cells for all treatment periods (6, 12, and 24 h) when
compared with control. Both carvacrol and thymol showed similar effects with the positive control
urethane on induction of the percentage of structural and total CA at the highest concentrations except
the effects of carvacrol for 6 h treatment (70 mg/kg b.w. and 100 mg/kg b.w., respectively). In
addition, carvacrol induced the numerical CA at all concentrations when compared to control and at
two highest concentrations (50 and 70 mg/kg b.w.) when compared to solvent control. Thymol also
induced the numerical CA especially at the highest concentration (100 mg/kg b.w.) for all treatment
periods.
Undeger et al. (2009) examined the genotoxicity of thymol and carvacrol using comet assay. V79
Chinese hamster lung fibroblast cells were treated with 1, 5, and 25 μM thymol and carvacrol. The
results of this study indicate a lack of clastogenic activity for thymol and carvacrol at biologically
relevant concentrations, and a moderate antioxidant activity in vitro.
Assessor’s comment:
The significance for risk assessment of the above findings with single components (thymol and others)
is somewhat difficult to interpret, because thymol seems to have both genotoxic and antigenotoxic
properties, depending on concentration and test system. The doses causing significant effects in the
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Thymus vulgaris
L.,
Thymus zygis
Loefl. ex. L., aetheroleum
EMA/HMPC/131903/2009
Page 14/19
study of Azirak and Rencuzugullari (2008) are at least 10 times higher than the estimated maximum
human dose (25 drops of an assumed size of 25 µl, resulting in 0.6 g of essential oil and calculated
doses of thymol and carvacrol as 4.7 and 0.34 mg/kg bw, respectively). Furthermore, the
administration in the study of Azirak and Rencuzugullari (2008) was intraperitoneal, which most
probably makes the difference between effective doses in rats and human posology even larger.
Reproduction toxicity:
Thyme essential oil consisting of 48% p-cymene and 24% thymol (0.25% essential oil in the feed over
2 weeks and during 4 days of pregnancy, n=15, number of embryos: 126) showed no influence on the
growth and development of mouse embryos in vivo (Domaracky et al. 2006).
3.3.1.
Assessor’s overall conclusions on toxicology
Potential mutagenicity and genotoxicity of thyme essential oil and its main components, especially
thymol, has been assessed in a number of studies on both prokaryotic and eukaryotic in vitro and in
vivo experimental systems. Studies have many weaknesses, findings are often contradictory and
reporting does not always contain sufficient details, which make interpretation difficult and conclusions
equivocal. Thymol is also an antioxidant and prevents DNA damage in certain experimental conditions.
It seems that in some studies thyme oil and its main components give weak indications towards
genotoxicity, but at the best these indications are weak and debatable. Adequately performed
mammalian cell studies are needed for the resolution of potential genotoxicity.
Although there is one of the strains of
S. typhimurium
lacking in the published AMES-test the data can
be regarded as sufficient for the development of a list entry for the cutaneous use of thyme oil and the
use as bath additive.
For a list entry for oral use data from an AMES-test fully complying with current guidelines are
considered to be necessary.
Nevertheless, thyme oil can be regarded as safe when administered in the recommended posology.
4.
Clinical Data
4.1.
Clinical Pharmacology
No data available.
4.1.1.
Overview of pharmacodynamic data regarding the herbal
substance(s)/preparation(s) including data on relevant constituents
No data available.
4.1.2.
Overview of pharmacokinetic data regarding the herbal
substance(s)/preparation(s) including data on relevant constituents
Thymol:
After application of a single dose of thyme dry extract (corresponding to 1.08 mg thymol) only the
sulfate could be detected in the human plasma, but not the free thymol nor the glucuronide. The
sulphate could be detected 20 minutes after application; maximum plasma levels were reached after
about 2 hours. Thymol can be detected in the plasma up to 38 hours; renal elimination was completed
within 24 hours. Elimination half-life was determined as 10.2 hours (Kohlert et al. 2002).
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Thymus zygis
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4.2.1.
Dose response studies
No data available.
4.2.2.
Clinical studies (case studies and clinical trials)
Indication: Cough associated with cold:
No data available from studies using thyme oil as the only active substance. Studies including
combinations with synthetic drugs are considered as not relevant for the monograph on thyme oil.
Stomatitis:
A comparison of different mouthrinses (containing thymol, chlorhexidine, povidon + H
2
O
2
) showed no
differences in the papillary bleeding score and in plaque index between the treatment with thymol and
water (Maruniak et al. 1992).
The application of a combination of thymol, menthol, methyl salicylate and 1.8-cineol over 6 months
did not show statistically significant differences between the vehicle and the essential oil group. Neither
development of bacterial resistance nor emergence of opportunistic pathogens could be observed
(Charles et al
.
2000).
Many clinical trials are published which investigate the efficacy of combinations of chlorhexidine and
thymol (e.g., Twetman et al
.
1999). The contribution of thymol to the overall efficacy cannot be
estimated.
4.2.3.
Clinical studies in special populations (e.g. elderly and children)
No data available.
4.3.
Overall conclusions on clinical pharmacology and efficacy
There are no clinical data available which would support the well-established use of thyme oil.
5.
Clinical Safety/Pharmacovigilance
5.1.
Overview of toxicological/safety data from clinical trials in humans
Case reports:
Germany has received 17 case reports for allergic reactions (urticaria, skin rashes, bronchospasm,
asthma attack, anaphylactic shock) concerning the use of thyme herb.
Austria: In the pharmacovigilance database of the Austrian medicines agency AGES PharmMed no
adverse events concerning
Thymus vulgaris
are reported (date 03.02.2009).
5.2.
Patient exposure
No data available.
5.3.
Adverse events
Adverse events related to the essential oil
2
In case of traditional use the long-standing use and experience should be assessed.
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In very rare cases allergic reactions may occur due to the content of thymol (Hänsel 1994).
Cross-sensitivity between plants belonging to the
Lamiaceae
family has been reported for the dust or
extracts (Benito et al. 1996). No such data are available for the essential oil.
In concentrations higher than 8% in Vaseline irritation of the skin may occur. The daily application in
gargles, mouthwashes and toothpastes over a longer period (no exact data available) may cause
allergic reactions (Hager CD-ROM 2008).
Adverse events related to thymol
Thymol has been used orally in folk medicine as a vermifuge at therapeutic doses (0.3 – 0.6 g, max. 1
g). Thymol in these concentrations caused abdominal pain and transient collapse (Czygan et al. 2004).
Assessor’s comment:
The symptoms described above may also be due to the worm infections. The doses of thymol
correspond to 62 – 208 g herbal substance. These doses exceed the recommended daily doses by far.
With the recommended amounts of thyme preparations only approximately 38 mg of thymol are
administered. The proposed dosage of the pure essential oil (25 drops per day) corresponds to
approximately 300 mg thymol. However, no adverse reactions from the oral use of the essential oil are
published.
Thymol has caused dermatitis in dentists and, when used in toothpaste, cheilitis and glossitis (Hager
CD-ROM 2008).
5.4.
Serious adverse events and deaths
Case reports:
Germany has received 17 case reports for allergic reactions including serious adverse events (urticaria,
skin rashes, bronchospasm, asthma attack, anaphylactic shock) concerning the use of thyme herb.
5.5.
Laboratory findings
No data available.
5.6.
Safety in special populations and situations
5.7.
Intrinsic (including elderly and children) /extrinsic factors
The German National Authority provided confidential data on the use of thyme oil as bath additive in
children. In an open multicenter post marketing surveillance study 491 children at an age from 1
month to 9 years suffering from acute or chronic infections of the upper airways were treated with
baths containing app. 12 mg thyme oil per litre. Although the study design does not allow conclusions
regarding the efficacy, the safety data might support the safe use of thyme oil in the paediatric
population.
Patients: 61 patients <= 6 months of age; 130 patients 6 - 12 months; 175 patients 12 - 24 months,
69 patients 24 - 36 months; 27 patients 36-48 months; 13 patients 48 - 60 months; 15 patients older,
1 child no age given.
Adverse events: In 7 cases (1.4%) a causal relationship between AE (skin irritation, mostly
exanthemas) and the study medication was rated as very likely. Unfortunately no data are available
about the age of the concerned patients.
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Skin irritation has to be rated as a common adverse event in the age group treated in this study. 92%
of the patients in this study were below 4 years of age. Some products authorized in Germany allow
the use in children up from 6 months of age.
Therefore the restriction to a minimum age of 3 years seems to be justified for the use of thyme oil as
bath additive.
For the oral use and for the cutaneous use no safety data from the paediatric population are available.
Additionally no data on the posology are published for children and adolescents. Therefore the oral and
cutaneous uses should be limited to adults and elderly.
Like other essential oils thyme oil should not be applied to the face particularly in the nasal area of
babies and infants under the age of two years because of the risk of a laryngospasm.
Full baths are contraindicated independent of the active substance in cases of large skin injuries, acute
skin diseases, high fever, severe infections, severe circulatory disturbances and cardiac insufficiency.
5.8.
Drug interactions
Topically applied thymol significantly enhanced the percutaneous absorption of 5-fluorouracil through
porcine epidermis in comparison with control (Gao et al. 1997).
Thyme oil potentiates the antifungal action of amphotericin B. The strongest decrease (48%) of the
MIC 80% was obtained with medium containing 0.2 μL/ mL of essential oil (Giordani et al. 2004).
Thyme oil increases the transdermal delivery of nitrendipine in two different skin models (Mittal et al.
2008).
5.9.
Use in pregnancy and lactation
Thyme essential oil consisting of 48% p-cymene and 24% thymol (0.25% essential oil in the feed over
2 weeks and during 4 days of pregnancy, n=15, number of embryos: 126) showed no influence on the
growth and development of mouse embryos in vivo (Domaracky et al. 2006).
In the absence of sufficient data the use during pregnancy and lactation is not recommended.
Single reports of hyperthyroidism are mentioned after long term use of overdoses of thymol.
No cases are reported for thyme oil.
5.11.
Drug abuse
Not relevant.
5.12.
Withdrawal and rebound
Not relevant.
5.13.
Effects on ability to drive or operate machinery or impairment of
mental ability
No studies on the effect on the ability to drive and use machines have been performed.
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5.14.
Overall conclusions on clinical safety
Thyme oil can be considered as safe when administered in the specified posology and the specified
route of administrations.
6.
Overall conclusions
Thyme oil is similarly used to thyme. Many beneficial effects have been attributed to thyme and its
essential oil throughout history but just a few have scientific evidence. There is no specified clinical
data available to support well-established use.
During the use of thyme oil spasmolytic, expectorant, antimicrobial, antioxidant, invigorating,
appetizing, eupeptic and choleretic properties have been experienced.
According to the traditional medicinal use the following indications are proposed:
Oral use:
Traditional herbal medicinal product used as an expectorant in cough associated with cold.
Cutaneous use, use as bath additive:
Traditional herbal medicinal product for the relief of symptoms in coughs and colds.
The lipophilic nature of the components of the essential oil makes absorption via the skin plausible. It
is also plausible that absorption of volatiles occurs after inhalation of the essential oil when applied in
semi-solid dosage forms, in a bath or in semi-solid dosage forms as embrocation.
Although there is one of the strains of
S. typhimurium
lacking in the published AMES-test the data can
be regarded as sufficient for the development of a list entry for the cutaneous use of thyme oil and the
use as bath additive.
For a list entry for oral use data from an AMES-test fully complying with current guidelines are
considered to be necessary.
Nevertheless, thyme oil can be regarded as safe when administered in the recommended posology.
Many clinical trials are published which investigate the efficacy of gargles consisting of combinations of
chlorhexidine and thymol. The contribution of thymol to the overall efficacy cannot be estimated. Since
the clinical evidence is only poorly documented for isolated compounds of the thyme essential oil or for
combinations with other essential oils and synthetic antiseptic drugs the traditional use of thyme oil as
a gargle cannot be supported.
The use against pruritus associated with dermatoses is not plausible.
Annex
List of references
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Thymus zygis
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Source: European Medicines Agency
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