Directorate C - Public Health and Risk Assessment
Adopted by the SCCP
during the 2
plenary meeting of 7 December 2004
Opinion on tea tree oil
1. BACKGROUND......................................................................................................... 3
2. TERMS OF REFERENCE.......................................................................................... 3
3. OPINION .................................................................................................................... 3
4. CONCLUSION ......................................................................................................... 18
OPINION ............................................................................................. 18
6. REFERENCES.......................................................................................................... 18
7. ACKNOWLEDGEMENTS ...................................................................................... 20
Tea Tree Oil and its components are not regulated in any of the annexes of the Cosmetic
In July 2003 the European Commission received a dossier on Tea Tree Oil provided by an Australian
Recently, the European Commission received
additional data on
the identity, purity,
contamination/impurities, toxicological data and allergies on the substance.
3.1. Chemical and Physical Specifications
The essential oil Tea Tree Oil is a complex mixture of compounds obtained by steam distillation
Sometimes, however, other essential oils from Leptospermum species and other Melaleuca
species may be summarised under this name, like for instance cajuput oil obtained from
Melaleuca leucadendra and niauli oil obtained from Melaleuca viridiflora. The European
Inventory contains 3 Melaleuca-type ingredients (INCI names): Melaleuca alternifolia oil
(antimicrobial), Melaleuca cajuputi extract (tonic), Melaleuca leucadendron extract (tonic).
Tea Tree Oil from Melaleuca alternifolia contains various mono- and sesquiterpenes as well as
γ-terpinene, α-terpinene, 1,8-cineole, p-
α-terpineol, α-pinene, terpinolenes, limonene and sabinene account for 80-90 % of the
oil. From about 100 terpenes found in Tea Tree Oil more than 60 individual substances have
been identified. The natural content of the individual terpenes in Tea Tree Oil may vary
considerably depending on the Melaleuca alternifolia population used, the climate, the leaf
maceration, the age of the leaves and the duration of distillation. For terpinen-4-ol the
concentrations measured varied from 28.6 % to 57.9 %, for
γ-terpinene from 9.5 % to 28.3 %,
α-terpinene from 4.6 % to 12.8 %, for 1.8-cineole from 0.5 % to 17.7 %, for p-cymene from
0.4 % to 12.4 %, for
enantiomeric composition of the principal components was analysed: for terpinen-4-ol the
enantiomeric ratio was 65:35 (+:-).
Ref.: 1, 2, 3, 4, 5, 6
In order to regulate the quality of Tea Tree Oil, requirements were imposed in the Australian
and in a former issue of the German Drugs Code (DAC) with respect to the level of individual
ingredients. The normative chromatographic profile set by ISO/FDIS 4730:2004 is given in
Ref.: 7, 8
Terpinen-4-ol 30 48
also when the oil is exposed to light and higher temperatures. The levels of
terpinene and terpinolene decrease whereas the level of p-cymene increases up to tenfold.
Oxidation processes lead to the formation of peroxides, endoperoxides and epoxides. The main
hydrolytic and oxidative degradation pathways are shown in Figure 1 (taken from Ref. 3).
was proven using a GC-MS analytical procedure.
As a further oxidation product 1,2,4-trihydroxymenthane was identified.
Melaleuca alternifolia oil (INCI)
Trade names and abbreviations
CAS / EINECS number
Terpinen-4-ol (41 %)
γ-Terpinene (19 %)
Colourless to pale liquid
See point 3.1.1.
Insoluble in water, miscible with ethanol 85% (v/v)
No data submitted
point : /
density at 20 °C
Refractive index at 20 °C
Tea Tree Oil is considered a universal remedy for acne, eczema, skin infections like herpes,
throat and gingival infections, haemorrhoids and vaginal infections. According to a recent
review on the use of plants in cosmetics Tea Tree Oil is widely employed in skin care for the
treatment of sores, blisters, spots, rashes, warts, burns and acne. Its antimicrobial activity is well
Ref.: 1, 2, 3, 11, 12, 13, 14
Tea Tree Oil is not currently subject to any constraint for the use in cosmetic products. It is sold
cosmetics, e.g. skin and body care products, toothpaste, mouthwash and in bath oils as well as in
products for aromatherapy. A monograph on Tea Tree Oil as an active ingredient being used in
cosmetic products was prepared in 2001 by the Norwegian delegation to the Council of Europe
Committee of experts on cosmetic products. The following cosmetic usage was evaluated: up to
0.5 % in toothpaste and mouth washes, up to 2 % in creams for chapped skin, hands and nails
and in deodorants, up to 3 % in bath preparations, shampoos and special detergents. The
Swedish MPA has registered three Tea Tree Oil containing products as "natural medicinal
In Germany, Tea Tree Oil does not have marketing authorisation as a pharmaceutical product
trials on the efficacy of pharmaceutical products. It can, however, be assumed that consumers
use Tea Tree Oil externally and internally for therapeutic purposes.
The European Cosmetic Toiletry and Perfumery Association (COLIPA) in 2002 published the
“COLIPA recommends that Tea Tree Oil should not be used in cosmetic products in a way that
Acute oral toxicity
Sprague Dawley rats
5 males + 5 females
Tea Tree Oil in peanut oil
0.83, 0.92, 1 ml/kg bw, once by gavage (SPF animals)
0.34, 0.43, 0.53, 0.56 0.6 ml/kg bw, once by gavage (non SPF animals)
Results SPF rats:
was calculated to be 2.6 ml (=
Results Non-SPF rats:
was calculated to be 1.9 ml (=1.7 mg) per kg
There are a few case reports of intoxication caused by Tea Tree Oil in humans.
A 4-year-old boy ingested a small quantity of Tea Tree Oil and became ataxic and progressed to
unresponsiveness. But 24 h after admission the child had recovered.
A 17-month-old male child developed ataxia and drowsiness following ingestion of less than 10
A 23-month-old boy became confused and was unable to walk 30 minutes after ingesting less
child was asymptomatic.
A man aged 60 swallowed about half a teaspoonful of Tea Tree Oil and had a dramatic rash
One person lapsed into a coma for 12 hours after ingesting half a cup of pure Tea Tree Oil and
Pursuant to § 16 Chemicals Act the predecessor of the German Federal Institute for Risk
Veterinary Medicine (BgVV) received a total of seven intoxication notifications involving Tea
Tree Oil between 1996 and 2002. In two infants symptoms of nausea, tiredness and vomiting
appeared following the oral intake of Tea Tree Oil; another infant did not develop any
symptoms. One adult suffered nausea, stomach pain, loss of appetite and eructation after taking
Tea Tree Oil capsules. In three other cases allergic reactions were observed after dermal
Acute dermal toxicity
Albino rabbits (NZ whites)
Tea Tree Oil
2000 mg/kg bw, once for 24 h
animals exhibited no signs of toxicity.
Acute inhalation toxicity
Albino rabbits (NZ whites)
The Draize irritation index was found to be 5.0, indicating a severe irritant.
solution was repeatedly applied over 30 days to the shaved rabbit skin. Minor initial irritations
declined; however, skin changes were found microscopically. In the patch test under semi-
occlusive conditions according to OECD 404, 12.5 % and 25 % Tea Tree Oil was not irritating,
while 50 % was minimally and 75 % Tea Tree Oil was slightly irritating in rabbits; undiluted
Tea Tree Oil in the patch test triggered irritations within 24 hours. For Tea Tree Oil the Draize
Index for skin irritation in rabbits was determined at 5.0.
Ref.: cited in 25
Tea Tree Oil has been investigated for skin irritancy using an occlusive patch test on 25 human
subjects for 21 days and compared with 1,8-cineole in concentrations of 0 %, 3.8 %, 8 %, 12 %,
16 %, 19.9 %, 24 %, and 28.1 % in soft white paraffin. 8 Tea Tree Oil preparations containing
similar 1,8-cineole concentrations (from 1.5 % to 28.8 %) and the 1,8-cineole-treated groups did
not show skin irritation. 3 of 28 panellists exhibited an allergic response. They were further
tested (see 4.3).
Mucous membrane irritation
Hen's egg test on the chorio-allantoic membrane (HET-CAM assay)
fertilised fresh chicken eggs (white leghorn)
substance treated 6, controls 2
Tea Tree Oil several oral products (see Table)
6081 and 871
(0.9% NaCl solution)
Tea Tree Oil
batch no. 6081
Tea Tree powder
water-soluble Tea Tree Oil
10 % surfactant
25 % Tea Tree Oil
5 % surfactant
5 % Tea Tree Oil
8 % surfactant
10 % Tea Tree Oil
10 % surfactant
Positive control (0.1 N NaOH)
Positive control (1 % SDS)
Neat Tea Tree Oil and 25 and 10 % solutions in surfactant as well as 10 % surfactant are severe
irritants in the assay while 5 % is only slightly effective. Tea Tree powder and ground leaf are
indicated and the reasoning of the used dilutions is not clear. Historical control data on the range
of response to positive control agents are included. The HET-CAM assay has been extensively
used and is showing promise as a potential alternative assay for eye irritation. However, it has
not yet been validated.
The method was based on the skin sensitisation study of Draize 1965. 6 Tea Tree Oil products
cream, ointment or gel formulation. Cream base was used as negative control. 151 adult male
and female panellists were selected. They gave their consent in conformance with the
Declaration of Helsinki. On day 1, 100 µl of the respective product was placed in Finn chambers
onto the upper arm or the back. After 48 h the chambers were removed and the skin was
assessed. If needed, the volunteers returned 48 h later for a further assessment. Skin reaction was
assessed on a 5-graded scale. The test products were applied to the skin 9 times over a 3 week
period and any response for irritancy was recorded (induction). After a 2 week rest phase the
products were applied on a new site (challenge). 2 days later and - if necessary - again after 4
days the skin reaction was assessed. Any doubtful results were repeated 2 weeks later.
0.1922 for the neat Tea Tree Oil. The other samples showed scores from 0.0000 to 0.0060.
150 of 151 panellists were evaluated. 3 out of 150 (2 %) became sensitized to
Tea Tree Oil.
In a second follow-up trial the number of panellists was increased to a joint number of 306
details were presented.
3 of 28 panellists of a skin irritancy study exhibited an allergic response to Tea Tree Oil. They
reactions were seen against a sesquiterpenoid hydrocarbon fraction and 1 against
1216 patients were patch tested in a Swiss dermatology clinic. 7 cases showed an allergic contact
fragrance-mix or colophony.
A case of positive patch testing with 1 % Tea Tree Oil solution was reported on a 74-year-old
An immediate systemic hypersensitivity reaction of a 38-year-old man associated with topical
finger and had applied this to psoriatic lesions on his leg.
A case of an allergic contact dermatitis to Tea Tree Oil with erythema multiforme-like ‘id’
reaction was reported.
A further case report of a contact allergy to Tea Tree Oil and cross-sensitization to colophony
origins from Norway.
In Wales a combined contact allergy to Tea Tree Oil and lavender oil complicating chronic
A case of contact dermatitis (face eczema) to Tea Tree Oil was reported which was explained by
α-terpinene, terpinolene and ascaridole.
7 patients were seen in a dermatology clinic during a 3-year period reactive to a 1 % solution of
α-terpinene and aromadendrene, 2 to
terpinen-4-ol and 1 to p-cymene and
Recently, contact dermatitis was observed with a 12-year-old boy who had applied Tea Tree Oil
The case reports in the literature were summarized and the potentially causative substances were
Ref.: 25, 38
In a Danish dermatology clinic from 2001-2002 (1. study) and in 2003 (2. study) 217 and 160
% Tea Tree Oil in petrolatum (study 1) and commercial lotions containing 5 % Tea Tree Oil
(study 1 and 2). In the 1
study only 1 person with a relevant positive patch test to 5 % and 10 %
study no allergic but 3.1 % (5/160) irritant reactions were seen.
In an Italian study of 725 consecutive patients were patch tested with undiluted, 5 %, 1 % and
to undiluted Tea Tree Oil only 1 patient was positive with the 1 % dilution, none with 0.1 %.
An increase in sensitization to oil of turpentine between 1992 and 1997 was found in a
departments of dermatology (IVDK). Oil of turpentine is a mixture of terpenes including
pinene, carenes and
0.5 % in the years 1996 and 1997 a dramatic increase was observed showing a sensitization rate
of 4.8 %. It was hypothesized that the increase in the use of Tea Tree Oil may be responsible due
to cross-reaction with turpentine.
In a parallel guinea-pig and human study freshly distilled as well as oxidised Tea Tree Oil and
Tea Tree Oil was demonstrated by an increase of the p-cymene content (2.0 % to 11.5 %)
accompanied by a decrease in the content of
α-terpinene (11.2 % to 5.0 %), γ-terpinene and
terpinolene. Simultaneously, the peroxide number increased from < 50 ppm to > 500 ppm.
All Tea Tree Oil-sensitive 11 patients reacted also positively to terpinolene, 9/11 to ascaridole
and 7/11 to
α-terpinene. Experimental sensitization in guinea pigs showed a low sensitizing
capacity for fresh Tea Tree Oil while photo-oxidised oil was revealed to be 3 times stronger
sensitizing. Also the monoterpene fraction obtained by fractional distillation elicited a positive
response as well as p-cymene.
1,2,4-Trihydroxymenthane was shown to be an oxidation product of Tea Tree Oil formed from
reacted positively to 1,2,4-trihydroxymenthane.
3 out of 28 normal healthy volunteers tested strongly positive to patch testing with Tea Tree Oil.
In the draft monograph submitted to the Council of Europe by the Norwegian delegation data of
Sweden was mentioned. The reports concerned mainly contact dermatitis and eczema (27 out of
33 cases). Only products having a concentration of 2 % or more seem to cause skin reactions.
In a multicenter study with 11 dermatological departments in Austria and Germany 36 out of
Great regional differences in frequencies were found (0 to 2.3 %). 10 of 10 positively tested
persons also reacted positive to terpinolene, ascaridole and
α-terpinene, 9 of 10 to 1,2,4-
trihydroxymenthane. 14 of these 36 persons (38.9 %) also showed a positive response to oil of
In a recent review on cutaneous effects of Tea Tree Oil prevalence rates for allergic contact
% reacted positively when patch-tested with Tea Tree Oil dilutions. Within the subjects with
previous exposure to Tea Tree Oil the rate rose to 4.3 to 7.2 %. The same authors report on
personal communications related to a study of the North American Contact Dermatitis Group.
0.5 % of patients reacted to oxidized Tea Tree Oil (5 % in petrolatum) on patch testing.
Allergic skin reactions related to oral intake of Tea Tree Oil have also been documented. After
oil. This resulted in obvious exacerbation of the dermatitis.
A case of Tea Tree Oil dermatitis associated with linear IgA disease was described. The patient
An airborne allergic contact dermatitis was observed following inhalation of the vapors of a hot
Repeated Dose (28 days) oral / dermal / inhalation toxicity
Sub-chronic (90 days) oral / dermal / inhalation toxicity
Chronic (> 12 months) toxicity
Reverse Mutation Testing Using Bacteria
Test substance :
Purity : no
Salmonella typhimurium TA98, TA100 and TA102
Vehicle : DMSO
S9 from rat liver homogenate (Aroclor 1254-induced)
Two generation reproduction toxicity
126.96.36.199. Phototoxicity / photoirritation and photosensitisation
188.8.131.52. Phototoxicity / photomutagenicity / photoclastogenicity
No data submitted
The in vitro cytotoxicity of Tea Tree Oil in cultured human epithelial and fibroblast cells was
toxicity in the neutral red bioassay.
Cases of Tea Tree Oil toxicosis have been reported in dogs and cats following dermal
weakness, incoordination, ataxia, muscle tremors etc.).
Ref.: 51, 52
In single-blinded randomized trial the treatment with a Tea Tree Oil shampoo was found to be
In clinical trials the efficacy of an aqueous gel with 5 % Tea Tree Oil was tested against acne
and compared with a 5 % benzoyl peroxide lotion. Like benzoyl peroxide, Tea Tree Oil induced
a significant reduction in inflamed and non-inflamed lesions. Side effects like smarting, itching,
dry skin and erythema were mentioned by 79 % of patients treated with benzoyl peroxide and 44
% of patients treated with Tea Tree Oil.
There are more publications on possible therapeutic uses and side reactions. They can be found
Safety evaluation (including calculation of the MoS)
At room temperature and under the influence of light and oxygen Tea Tree Oil was shown to
increase. In addition, oxidation processes lead to the formation of peroxides, endoperoxides and
Acute toxicity data is available for Tea Tree Oil. The LD
after oral application amounts to 1.9
to 2.6 g per kg body weight in rats depending on the strain examined. In rabbits no toxic effects
were observed after dermal application of up to 2 g per kg body weight. There are a few case
reports of intoxication caused by Tea Tree Oil in humans.
No experimental data on percutaneous absorption were provided. But, due to the lipophilic
is confirmed by systemic neurotoxic reactions following topical application.
No data on repeated dose toxicity, subchronic and chronic toxicity, carcinogenicity and
(Ames test). No conclusion can be drawn as to the mutagenicity and carcinogenicity of Tea Tree
Oil. Since no data on percutaneous absorption and subchronic toxicity are available no safety
evaluation can be performed.
Undiluted Tea Tree Oil is a severe irritant to the skin of rabbits while a 25 % solution is not. In a
irritants in the assay while 5 % is only slightly irritant.
Neat Tea Tree Oil is a sensitiser in humans. In a study including 9 treatments, 3 of 150
volunteers became sensitized.
The prevalence for allergic contact dermatitis exhibits regional differences. In a Swiss study 7 of
11 dermatological departments in Austria and Germany 36 out of 3375 patients (1.1 %) reacted
positive to a 5 % solution of Tea Tree Oil. It is not fully understood which of the constituents is
degradation products like ascaridole, 1,2,4-trihydroxymethane, peroxides and epoxides were
discussed. Oxidised Tea Tree Oil is 3 times more potent than fresh oil. The sensitising potency
may also be influenced by the content of irritants such as p-cymene and 1,8-cineole. Only
products having a concentration of 2 % or more seem to cause skin reactions.
The sparse data available suggest that the use of undiluted Tea Tree Oil as a commercial product
The stability of Tea Tree Oil in cosmetic formulations is questionable. A standardized method
for the specification of Tea Tree Oil is needed. Industry should develop an analytical testing
method based on typical degradation products to ensure and control the stability of the material.
Skin and eye irritation was not assessed by adequate methods. There are relevant data gaps with
reproductive toxicity. The safe use of Tea Tree Oil as cosmetic ingredient cannot be assessed.
A complete dossier of a representative standardized material to all relevant toxicological
time will be given.
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Members of the working group are acknowledged for their valuable contribution to this opinion.
Dr. C. Chambers
Prof. C. Galli
Prof. J. Krutmann
Prof. J.-P. Marty
Prof. T. Platzek
Dr. S. Rastogi
Prof. J. Revuz
Prof. V. Rogiers
Prof. T. Sanner
Dr. J. van Engelen