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Directorate C - Public Health and Risk Assessment 

C7 - Risk assessment 






















Opinion on  





Tea Tree Oil 

















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 




Opinion on tea tree oil 








Tea Tree Oil and its components are not regulated in any of the annexes of the Cosmetic 

Directive 76/768/EEC.  


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. 


2.  T




On the basis of provided data the SCCP is asked to assess the risk to consumer when Tea 


Tree Oil is used in cosmetic products? 


Does the SCCP propose any restrictions or conditions for the use of Tea Tree Oil as an 




Does the SCCP propose any restrictions or conditions in terms of concentrations for the 


use of Tea Tree Oil in cosmetic products? 


Does the SCCP find it important, for safety reasons, to have a date of minimum durability 


on the Tea Tree Oil products? 







3.1.  Chemical and Physical Specifications 



Chemical  identity 


The essential oil Tea Tree Oil is a complex mixture of compounds obtained by steam distillation 

from the leaves and twigs of the Australian tea tree (Melaleuca alternifolia, Myrtaceae). 

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 

aromatic compounds. The monoterpenes terpinen-4-ol, 

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 


Opinion on tea tree oil 



0.4 % to 12.4 %, for 

α-terpineol from 1.5 % to 7.6 % and for limonene from 0.4 % to 3.1 %. The 

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 

Standard, in the International Standard ISO 4730 (ISO 4730, 1996 and ISO/FDIS 4730, 2004) 

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 

Table 1. 

Ref.: 7, 8 



Table 1:  Chromatographic profile of Tea Tree Oil according to ISO/FDIS 4730:2004 


Component Minimum 





1 6 

Sabinene trace 



5 13 

Limonene 0.5 


p-Cymene 0.5 

1,8-Cineole (eucalyptol) 




10 28 

Terpinolene 1.5 

Terpinen-4-ol 30 48 


1.5 8 

Aromadendrene trace 3 

Ledene (syn. 


trace 3 


trace 3 

Globulol trace 

Viridiflorol trace 



The composition of Tea Tree Oil changes particularly in the presence of atmospheric oxygen but 

also when the oil is exposed to light and higher temperatures. The levels of 

α-terpinene,  γ-

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). 



Opinion on tea tree oil 






γ-Terpinene  α-Terpinolene 

















Figure 1:  End products of hydrolysis and oxidation of Tea Tree Oil constituents 



In Tea Tree Oil stored for 9 months under sunlight the formation of the endoperoxide ascaridole 

was proven using a GC-MS analytical procedure. 

Ref.: 9 


As a further oxidation product 1,2,4-trihydroxymenthane was identified.  

Ref.: 10 





Opinion on tea tree oil 












3.1.1. 1. 

Primary name and/or INCI name 


Melaleuca alternifolia oil (INCI)   Chemical 



Not applicable 


Trade names and abbreviations 



CAS / EINECS number 


CAS no.:   


EINECS no.: 

285-377-1   Structural 



main constituents: 





Terpinen-4-ol (41 %) 

γ-Terpinene (19 %)    Empirical 



not applicable 




Opinion on tea tree oil 




Physical  form 


Colourless to pale liquid 



Molecular  weight 


Not applicable 



Purity, composition and substance codes 


See point 3.1.1. 



Impurities / accompanying contaminants 


See point 3.1.1. 





Insoluble in water, miscible with ethanol 85% (v/v) 



Partition coefficient (Log P



No data submitted 



Additional physical and chemical specifications 


organoleptic properties  

myristic odour 

- flash 


   : / 

- vapour 


  : / 

- boiling 

point   : / 

density at 20 °C   



- viscosity 

   : / 





UV absorption spectrum 

Refractive index at 20 °C 


Ref.: 8 



3.2.  Function and uses 


Tea Tree Oil is considered a universal remedy for acne, eczema, skin infections like herpes, 

wounds, warts, burns, insect bites and nail mycosis. Other indications mentioned are colds, sore 

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 



Opinion on tea tree oil 



Tea Tree Oil is not currently subject to any constraint for the use in cosmetic products. It is sold 

undiluted and highly concentrated to the public. Furthermore, the oil is used as ingredient of 

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 


Ref.: 15 


In Germany, Tea Tree Oil does not have marketing authorisation as a pharmaceutical product 

since a positive clinical effect has not yet been proven according to valid criteria for clinical 

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 

following recommendation: 


COLIPA recommends that Tea Tree Oil should not be used in cosmetic products in a way that 

results in a concentration greater than 1 % oil being applied to the body. When formulating Tea 

Tree Oil in a cosmetic product, companies should consider that the sensitisation potential 

increases if certain constituents of the oil become oxidised. To reduce the formation of these 

oxidation products, manufacturers should consider the use of antioxidants and/or specific 

packaging to minimise exposure to light. 




3.3. Toxicological 




Acute  toxicity 


Acute oral toxicity 




Sprague Dawley rats 

Group size   

5 males + 5 females 

Test substance  : 

Tea Tree Oil in peanut oil 

Batch no   


Purity  : / 



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: 

Animals exhibited lack of tonus in the forelimbs. The LD


 was calculated to be 2.6 ml (= 

2.3 mg) per kg bw. 


Opinion on tea tree oil 



Results Non-SPF rats: 

The animals showed similar symptoms. The LD


 was calculated to be 1.9 ml (=1.7 mg) per kg 


Ref.: 16 



Reports on human poisoning 


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. 

Ref.: 17 


A 17-month-old male child developed ataxia and drowsiness following ingestion of less than 10 

ml Tea Tree Oil. 

Ref.: 18 


A 23-month-old boy became confused and was unable to walk 30 minutes after ingesting less 

than 10 ml of a commercial product containing 100 % melaleuca oil. 5 h following ingestion the 

child was asymptomatic. 

Ref.: 19 


A man aged 60 swallowed about half a teaspoonful of Tea Tree Oil and had a dramatic rash 

accompanied by leukocytosis. 

Ref.: 20 


One person lapsed into a coma for 12 hours after ingesting half a cup of pure Tea Tree Oil and 

suffered disturbances of consciousness for another 36 hours. 

Ref.: 21 


Pursuant to § 16 Chemicals Act the predecessor of the German Federal Institute for Risk 

Assessment (BfR), the former Federal Institute for Health Protection of Consumers and 

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 


Ref.: 22 


Acute dermal toxicity 



OECD 402 


Albino rabbits (NZ whites) 

Group size   

5 males + 5 females 

Test substance  : 

Tea Tree Oil 

Batch no   


Purity  : / 


Opinion on tea tree oil 





2000 mg/kg bw, once for 24 h 


  : not 





The animals were observed for 14 d. With the exception of slight diarrhoea (1 animal) the 

animals exhibited no signs of toxicity. 

Ref.: 23 


Acute inhalation toxicity 


No data submitted 



Irritation and corrosivity   Skin 





Albino rabbits (NZ whites)  

Group size   

Test substance  : 

Tea Tree Oil 

Batch No.   


Purity  : / 


  : 0.5 




not in compliance  


The Draize irritation index was found to be 5.0, indicating a severe irritant. 

Ref.: 24 



A skin irritation test in rabbits was conducted with 25 % Tea Tree Oil in paraffin oil and the 

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 



Human study 


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). 

Ref.: 26 


Opinion on tea tree oil 




Mucous membrane irritation 


Hen's egg test on the chorio-allantoic membrane (HET-CAM assay) 




fertilised fresh chicken eggs (white leghorn) 

Group size   

substance treated 6, controls 2  

Test substance  : 

Tea Tree Oil several oral products (see Table) 

Batch number 

6081 and 871 

Purity  : pharmaceutical 




0.1 g / egg, controls: 300 µl / egg. 


  : In 





Substance Mean 




Negative control 

(0.9% NaCl solution) 

0.0 non-irritant 

Tea Tree Oil 

batch no. 6081 

16.1 severe 

Tea Tree powder 



Tea Tree ground leaf 



water-soluble Tea Tree Oil 



Placebo (0 % Tea Tree Oil) 

10 % surfactant 

10.3 severe 

25 % Tea Tree Oil 

5 % surfactant 

9.8 severe 

5 % Tea Tree Oil 

8 % surfactant 

4.5 slight 

10 % Tea Tree Oil 

10 % surfactant 

12.1 severe 

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 




The description of the analysed substances is poor. The identity of the used surfactant is not 

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. 

Ref.: 27 



Skin  sensitisation 


Opinion on tea tree oil 




Human studies 


The method was based on the skin sensitisation study of Draize 1965. 6 Tea Tree Oil products 

were investigated which consisted of 100 % Tea Tree Oil and 25 % and 5 % Tea Tree Oil in 

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. 



Irritancy:  148 of 151 panellists were evaluated. The average daily score for irritancy was 

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 

(irritancy) and 308 (sensitization). The second study confirmed the results of the first one but no 

details were presented. 

Ref.: 28 


3 of 28 panellists of a skin irritancy study exhibited an allergic response to Tea Tree Oil. They 

were further tested for allergic responses with major constituents of Tea Tree Oil. 3 positive 

reactions were seen against a sesquiterpenoid hydrocarbon fraction and 1 against 


Ref.: 26 


1216 patients were patch tested in a Swiss dermatology clinic. 7 cases showed an allergic contact 

dermatitis due to Tea Tree Oil while 2 of them also exhibited a type IV hypersensitivity towards 

fragrance-mix or colophony. 

Ref.: 29 


A case of positive patch testing with 1 % Tea Tree Oil solution was reported on a 74-year-old 

man with a history of blistering dermatitis who had treated warts with Tea Tree Oil as wart paint. 

Ref.: 30 


An immediate systemic hypersensitivity reaction of a 38-year-old man associated with topical 

application of Tea Tree Oil was observed. The patient had placed a drop of Tea Tree Oil on his 

finger and had applied this to psoriatic lesions on his leg. 

Ref.: 31 




A case of an allergic contact dermatitis to Tea Tree Oil with erythema multiforme-like ‘id’ 

reaction was reported. 


Opinion on tea tree oil 



Ref.: 32 


A further case report of a contact allergy to Tea Tree Oil and cross-sensitization to colophony 

origins from Norway. 

Ref.: 33 


In Wales a combined contact allergy to Tea Tree Oil and lavender oil complicating chronic 

vulvovaginitis was observed. 

Ref.: 34 


A case of contact dermatitis (face eczema) to Tea Tree Oil was reported which was explained by 

the use of Tea Tree Oil against pimples. The epicutaneous testing of the patient revealed positive 

reactions to 

α-terpinene, terpinolene and ascaridole. 

Ref.: 35 


7 patients were seen in a dermatology clinic during a 3-year period reactive to a 1 % solution of 

melaleuca oil. 6 of them also reacted to limonene, 5 to 

α-terpinene and aromadendrene, 2 to 

terpinen-4-ol and 1 to p-cymene and 


Ref.: 36 


Recently, contact dermatitis was observed with a 12-year-old boy who had applied Tea Tree Oil 

on his face to treat a minimal skin infection. 

Ref.: 37 


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 

consecutive patients were patch tested with the European standard series and in addition with 10 

% 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 % 

neat Tree Oil. In the 2


 study no allergic but 3.1 % (5/160) irritant reactions were seen.  

Ref.: 39 


In an Italian study of 725 consecutive patients were patch tested with undiluted, 5 %, 1 % and 

0.1 % Tea Tree Oil in petrolatum. While in 5.9 % of the patient positive reactions were observed 

to undiluted Tea Tree Oil only 1 patient was positive with the 1 % dilution, none with 0.1 %. 

Ref.: 40 


An increase in sensitization to oil of turpentine between 1992 and 1997 was found in a 

multicenter study on 45,005 patients from the German-Austrian information network of 

departments of dermatology (IVDK). Oil of turpentine is a mixture of terpenes including 


pinene, carenes and 

β-pinene. While between 1992 and 1995 the prevalence rate was as low as 

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. 

Ref.: 41 



Opinion on tea tree oil 



In a parallel guinea-pig and human study freshly distilled as well as oxidised Tea Tree Oil and 

some fractions were analysed and compared as to their sensitizing properties. Photo-oxidation of 

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. 

Ref.: 42 


1,2,4-Trihydroxymenthane was shown to be an oxidation product of Tea Tree Oil formed from 

terpinen-4-ol. By epicutaneous patch testing of 15 patients sensitive to Tea Tree Oil 11 of them 

reacted positively to 1,2,4-trihydroxymenthane. 

Ref.: 10 


3 out of 28 normal healthy volunteers tested strongly positive to patch testing with Tea Tree Oil. 

All 3 reacted positive to a sesquiterpenoid fraction of the oil, 1 of them to 


Ref.: 43 


In the draft monograph submitted to the Council of Europe by the Norwegian delegation data of 

the Swedish MPA (Medicinal Products Agency) on adverse effects induced by Tea Tree Oil in 

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. 

Ref.: 15 


In a multicenter study with 11 dermatological departments in Austria and Germany 36 out of 

3375 patients (1.1 %) reacted positive to a 5 % solution of Tea Tree Oil in diethylphthalate. 

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 


Ref.: 44 


In a recent review on cutaneous effects of Tea Tree Oil prevalence rates for allergic contact 

dermatitis reactions were cited. In an Australian study conducted with 219 volunteers 2.9 to 4.8 

% 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. 

Ref.: 45 


Allergic skin reactions related to oral intake of Tea Tree Oil have also been documented. After 

initial external treatment of an atopic dermatitis with undiluted Tea Tree Oil a man ingested the 

oil. This resulted in obvious exacerbation of the dermatitis. 

Ref.: 46 



Opinion on tea tree oil 



A case of Tea Tree Oil dermatitis associated with linear IgA disease was described. The patient 

had applied Tea Tree Oil to her recently pierced umbilicus. 

Ref.: 47 


An airborne allergic contact dermatitis was observed following inhalation of the vapors of a hot 

aqueous solution of Tea Tree Oil. 

Ref.: 48 



Dermal / percutaneous absorption 


No data submitted 



Repeated dose toxicity 


Repeated Dose (28 days) oral / dermal / inhalation toxicity 


No data submitted 


Sub-chronic (90 days) oral / dermal / inhalation toxicity 


No data submitted 


Chronic (> 12 months) toxicity 


No data submitted 



Mutagenicity / Genotoxicity 


Reverse Mutation Testing Using Bacteria 



Test substance  : 

Tea Tree Oil 

Batch no   

Purity  : no 


Test system 

Salmonella typhimurium TA98, TA100 and TA102 

Vehicle   :  DMSO 

Metabolic act. 

S9 from rat liver homogenate (Aroclor 1254-induced) 



100, 250, 500, 100, 1500 µg per plate 




  : / 




No sufficient details were reported, the study is inadequate. 



Tea Tree Oil has antimicrobial properties. Therefore, the test is of limited value. 

Ref.: 49 


Opinion on tea tree oil 







No data submitted 



Reproductive  toxicity 


Two generation reproduction toxicity 


No data submitted   Teratogenicity 


No data submitted 





No data submitted 


3.3.10.   Photo-induced 

toxicity  Phototoxicity / photoirritation and photosensitisation 


No data submitted  Phototoxicity / photomutagenicity / photoclastogenicity 


No data submitted 


3.3.11.   Human 



 No data submitted 


3.3.12.   Special 



The in vitro cytotoxicity of Tea Tree Oil in cultured human epithelial and fibroblast cells was 

investigated and compared with three resin acid analogues. Tea Tree Oil showed a lower level of 

toxicity in the neutral red bioassay. 

Ref.: 50 


Cases of Tea Tree Oil toxicosis have been reported in dogs and cats following dermal 

application for therapeutic reasons. Typical signs of neurotoxicity were observed (depression, 

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 

more effective against dandruff than a placebo shampoo.  


Opinion on tea tree oil 



Ref.: 53 


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. 

Ref.: 54 


There are more publications on possible therapeutic uses and side reactions. They can be found 

in a recent review.  

Ref.: 45 




Safety evaluation (including calculation of the MoS) 


Not applicable 


3.3.14. Discussion 


At room temperature and under the influence of light and oxygen Tea Tree Oil was shown to 

degrade rapidly. Under these conditions the p-cymene and terpinen-4-ol contents considerably 

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 

nature of the main constituents it is assumed that they are readily absorbed through the skin. This 

is confirmed by systemic neurotoxic reactions following topical application. 


No data on repeated dose toxicity, subchronic and chronic toxicity, carcinogenicity and 

reproductive toxicity are available. Only one inadequate study on genotoxicity was provided 

(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 

HET-CAM assay neat Tea Tree Oil as well as 25 and 10 % solutions in surfactant are severe 

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 

1216 (0.6 %) patch tested patients reacted positive to Tea Tree Oil. In a multicenter study with 

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 


Opinion on tea tree oil 



responsible. Terpinolene, 

α-terpinene, a sesquiterpenoid fraction, limonene and/or oxidative 

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 

is not safe. The safety dossier of Tea Tree Oil is incomplete.  

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 

regard to subchronic toxicity, percutaneous absorption, genotoxicity/carcinogenicity and 

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 

endpoints is required by the end of 2005; an opinion based on the information available at that 

time will be given. 







Not applicable 







1.  Saller R, Reichling J (1995) Teebaum-Öl. Ein natürliches Universalheilmittel? Deut 


Apotheker Z 135: 40-48 


Galle-Hoffmann U, König WA (1999) Ätherische Öle - Teebaumöl. Deut Apotheker Z 



3.  Jarmyn RJ (1998) Vielseitig aber eigensinnig. Teebaumöl in Kosmetika und 


Körperpflegeprodukten. Parfümerie und Kosmetik 79: 22-6 

4.  Leach DN, Wyllie SG, Hall JG, Kyratzis I (1993) Enantiomeric composition of the 


principal components of the oil of Melaleuca alternifolia. J Agric Food Chem 41: 627-32 

5.  Johns MR, Johns JE, Rudolph V (1992) Steam distillation of tea tree (Melaleuca 

 alternifolia) oil. J Sci Food Agric 58: 49-53 


Brophy JJ, Davies NW, Southwell IA, Stiff IA, Williams LR (1989) Gas chromatographic 


quality control for oil of melaleuca terpinen-4-ol type (Australian tea tree). J Agric Food 


Chem 37: 1330-5 


International Organisation for Standardisation. ISO 4730 (1996) International Standard Oil 


of Melaleuca, terpinen-4-ol type (Tea Tree oil) 

8.  International Organisation for Standardisation. ISO/FDIS 4730 (2004) Final draft, 


International Standard Oil of Meleleuca, terpinen-4-ol type (Tea Tree oil) 


Opinion on tea tree oil 




Harkenthal M, Reichling J, Geiss HK, Saller R (1998) Oxidationsprodukte als mögliche 


Ursache von Kontaktdermatitiden. Pharmazeut Z 47: 4092 

10.  Harkenthal M, Hausen BM, Reichling J (2000) 1,2,4-Trihydroxy menthane, a contact 


allergen from oxidized Australian tea tree oil. Pharmazie 55: 153-4 

11.  Osborne F, Chandler F (1998) Australian tea tree oil. Canadian Pharmaceut J 131: 42-46 

12.  Aburjai T, Natsheh FM (2003) Plants used in cosmetics. Phytotherapy Res 17: 987-1000 

13.  Carson CF, Riley TV (1993) Antimicrobial activity of the essential oil of Melaleuca 


alternifolia. Lett Appl Microbiol 16: 49-55 

14.  Carson CF, Riley TV (1994) The antimicrobial activity of the tea tree oil. Med J Australia 



15.  NN (2001) Tea Tree Oil (TTO) Monograph on active ingredient being used in cosmetic 


products, prepared by the Norwegian delegation to the Council of Europe Committee of 


experts on cosmetic products, RD 4-3/35. 

16.  Bolt AG (1989) Final report, acute oral toxicity of tea tree oil in the rat. Pharmaceutical 



17.  Morris M, Donoghue A, Markovitz J, Osterhoudt K (2003) Ingestion of tea tree oil 


(Melaleuca oil) by 4-year-old boy. Pediat Emergency Care 19: 169-171 

18.  del Beccaro MA (1995) Melaleuca oil poisoning in a 17-month-old. Vet Hum Toxicol 37: 


19.  Jacobs MR, Hornfeldt CS (1994) Melaleuca oil poisoning. Clin Toxicol 32: 461-464 

20.  Elliott C (1993) Tea tree oil poisoning. Med J Aust 159: 830-831 

21.  Carson CF, Riley TV (1995) Toxicity of the essential oil Melaleuca alternifolia or tea tree 


oil. Clin Toxicol 33: 193-194 

22.  Ärztliche Mitteilungen bei Vergiftungen 1990-1995, 2000, 2001, BgVV-Schriften,


23.  Bolt AG (1989) Final report, acute dermal toxicity limit test of tea tree oil batch 88/375 in 


the rabbit. Pharmaceutical Consulting Service  

24.  Bolt AG (1989) Final report, acute dermal irritation of tea tree oil batch 88/375 in the 


rabbit. Pharmaceutical Consulting Service  

25.  Beckmann B, Ippen H (1998) Teebaum-Öl. Dermatosen 46: 120-124 

26.  Southwell IA, Freeman S, Rubel D (1997) Skin irritancy of tea tree oil. J Essent Oil Res 9: 


27.  Leuschner J (1998) Screening of several oral tea tree oil PG-premium products for the eye 


irritancy potential using fertile chicken eggs HET-CAM-test in vitro. Laboratory of 


pharmacology and toxicology, Hamburg, Germany  

28.  NN (1997) Human studies Draize method, study no. DT-029. Skin& Cancer Foundation 



29.  Fritz T-M, Burg G, Krasovec M (2001) Allergic contact dermatitis to cosmetics containing 


Melaleuca alternifolia (tea tree oil). Ann Dermatol Venereol 128: 123-126 

30.  Bhushan M, Beck MH (1997) Allergic contact dermatitis from tea tree oil in a wart paint. 


Contact Dermatitis 36: 117-118 

31.  Mozelsio NB, Harris KE, McGrath KG, Grammer LC (2003) Immediate systemic 


hypersensitivity reaction associated with topical application of australian tee tree oil. 


Allergy Asthma 24: 73-75 

32.  Khanna M, Qasem K, Sasseville D (2000) Allergic contact dermatitis to tea tree oil with 


erythema multiforme-like Id reaction. Amer J Cont Derm 11: 238-42 

33.  Selvaag E, Eriksen B, Thune P (1994) Contact allergy due to tea tree oil and cross-


sensitization to colophony. Contact Dermatitis 31: 124 


Opinion on tea tree oil 



34.  Varma S, Blackford S, Statham BN, Blackwell A (2000) Combined contact allergy to tea 


tree oil and lavender oil complicating chronic vulvovaginitis. Contact Derm. 42: 309-310 

35.  Knight TE, Hausen BM (1994) Melaleuca oil (tea tree oil) dermatitis. J Amer Acad 


Dermatol 30: 423-7 

36.  Hausen BM (1998) Kontaktallergie auf Teebaumöl und Ascaridol. Akt Dermatol 24: 60-62 

37.  Kütting B, Brehler R, Traupe H (2004) Allergic contact dermatitis in children - strategies 


of prevention and risk management. Eur J Dermatol 14: 80-85 

38.  Hausen BM (1999) "Wundermittel" mit Tücken:  Teebaumöl. Ärzt Prax Dermatol 9-10: 27 

39.  Veien NK, Rosner K, Skovgaard GL (2004) Is tea tree oil an important contact allergen? 


Contact Dermatitis 50: 378-379  

40.  Lisi P, Melingi L, Pigatto P, Ayala F, Suppa F, Foti C, Angelini G (2000) Prevalenza della 


sensibilizzazione all´olio essenziale  di Melaleuca. Ann Ital Dermatol Allergol 54: 141-144 

41.  Treudler R, Richter G, Geier J, Schnuch A, Orfanos CE, Tebbe B (2000) Increase in 


sensitisation to oil of turpentine: Recent data from a Multicenter Study on 45,005 patients 


from the German-Austrian Information Network of Departments of Dermatology (IVDK). 


Contact Dermatitis 42: 68-73 

42.  Hausen BM, Reichling J, Harkenthal M (1999) Degradation products of monoterpenes are 


the sensitizing agents in tea tree oil. Amer J Cont Derm 10: 68-77 

43.  Rubel DM, Freeman S, Southwell IA (1998) Tea tree oil allergy: What is the offending 


agent? Report of three cases of tea tree oil allergy and review of the literature. Aust J Derm 



44.  Pirker C, Hausen BM, Uter W, Hillen U, Brasch J, Bayerl C, Lippert U, Fuchs Th, Aberer 


W, Fartasch M, Tebbe B, Richter G, Kinaciyan T, Frosch PJ (2003) Sensibilisierung auf 


Teebaumöl in Deutschland und Österreich - Eine multizentrische Studie der Deutschen 


Kontaktallergiegruppe. J Deut Dermatol Ges 1: 629-34 

45.  Crawford GH,  Sciacca JR, James WD (2004) Tea tree oil: cutaneous effect of the 


extracted oil of Melaleuca alternifolia. Dermatitis 15: 59-66 


46.  de Groot AC, Weyland JW (1992) Systemic contact dermatitis from tea tree oil. Contact 

Dermatitis 27: 279-80 

47.  Perrett CM, Evans AV, Russell-Jones R (2003) Tea tree oil dermatitis associated with 


linear IgA disease. Clin Exp Derm 28: 167-170 

48.  de Groot AC (1996) Airborne allergic contact dermatitis from tea tree oil. Contact 


Dermatitis 35: 304-5 

49.  Davey RB (1989) Final report. The activity of Tea Tree Oil in the Ames test. 


Pharmaceutical Consulting Services  

50.  Söderberg TA, Johansson A, Gref R (1996) Toxic effects of some conifer resin acids and 


tea tree oil on human epithelial and fibroblast cells. Toxicology 107: 99-109 

51.  Villar D, Knight MJ, Hansen SR, Buck WB (1994) Toxicity of Melaleuca Oil and related 


essential oils applied topically on dogs and cats. Vet Human Toxicol 36: 139-142 

52.  Bischoff K, Guale F (1998) Australian tea tree (Melaleuca alternifolia) oil poisoning in 


three purebred cats. J Vet Diagnost Invest 10: 208-210 

53.  Satchell AC, Saurajen A, Bell C, Barnetson RS (2002) Treatment of dandruff with 5% tea 


tree oil shampoo. J Amer Acad Dermatol 47: 852-855 

54.  Bassett IB, Pannowitz DL, Barnetson RSTC (1990) A comparitive study of tea-tree oil 


versus benzoylperoxide in the treatment of acne. Med J Austral 153: 455-457 








Opinion on tea tree oil 



Members of the working group are acknowledged for their valuable contribution to this opinion. 

The members of the working group are: 


Dr. C. Chambers 

Prof. G. Degen 

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 

Dr. I.R. White 


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