THE FIRST TRULY INDEPENDENT WATCHDOG FOR THOSE WORKING WITH NATURAL AROMATIC MATERIALS
To: Mr P. Wagstaffe,
Head of Unit,
Health and Consumer Protection Directorate-General
Dear Mr Wagstaffe,
Re : SCCP Opinion on Tea Tree Oil (SCCP/0843/04).
Cropwatch is an Independent Watchdog for Natural Aromatic Products used in the Aroma (Perfumes, Flavours, Aromatherapy, Cosmetics), Herbal, Traditional Medicine & Phytochemical Industries. Drawing on academic and professional opinions from those employed in appropriate corporate industries and relevant NGO and governmental bodies, Cropwatch is able to give voice to views, which would possibly otherwise remain unheard.
The purpose of this letter is:
At present Cropwatch is gathering adverse effect data from various end-users including practising aromatherapists via their professional organisations, who may have administered thousands of treatments using tea tree oil over periods of up to 15 years. It is believed that the incidence of tea tree sensitisation from data supplied by such users will prove to be exceedingly small.
Most aromatherapy end-users are trained to use essential oils diluted in vegetable carrier oil, something that is a message also impressed on the general public. Best practice in aromatherapy massage typically uses essential oil concentrations from 0.5% to 2.5% v/v in fixed vegetable massage oils, with the lower concentrations being used for children and elderly people. The use of neat oils is unsupported by professional aromatherapy organisations. Aromatherapists, as well as members of the general public are reported as applying undiluted essential oils to the skin in certain ‘minor emergency’ situations – tea tree oil for small skin traumas, lavender oil for very minor burn areas, cajuput (Melaleuca cajuputi Powell) or niaouli oils (Melaleuca quinquenervia (Cav.) S.T. Blake) for insect bites, stings etc. etc. Here the benefits of direct application of neat oil in an emergency are judged to outweigh risks from any inflammatory response.
For example, at a time when morbidity and mortality due to hospital-acquired infections is a primary health care issue (mainly acquired via hand-carried staff-patient or patient-patient transmissions (Messanger et al. 2005)), then tea tree oil - which is potentially active against MRSA – may have an important role to play in prevention. Furthermore, the authors of a study looking at the anti-microbiological effectiveness of handwashes incorporating tea tree oil (Messanger et al. 2005) found that they did not cause the dermatological problems associated with other products. In apparent support of this, Greig (1999) had previously established a case of allergic dermatitis following use of a tea tree handwash was not due to the tea tree oil content. It would be most unfortunate if the public availability of tea tree oil (e.g. for use in handwashing products which can help prevent pathogen transmission) was ultimately be governed by some somewhat inappropriate cosmetic regulation.
In particular, it is thought that the make-up of the expert panel of the SCCP committee would benefit in the public eye from the inclusion of a member who, say, had a positive view on the healing properties of tea tree oil, gained from their regular experience of the item’s use in therapy, or from dermatologists who have been critical of previous EU legislation based on SCCNFP Opinion [such as Professor Axel Schnuch – see Schnuch (2005)]. Cropwatch feels that this move is urgently needed to help counterbalance the views of certain identifiable SCCP committee members with well-known negative (some would say distinctly prejudicial) views on the alleged adverse health effects of fragrance materials.
3. Cropwatch needs time to address credibility gaps in the SCCP Opinion on tea tree oil, via a full critique of the science presented. Aside from a group of eminent academics apparently being unable to provide the up-to-date botanical nomenclature for essential oils from Melaleuca species in the Opinion, the more serious issues include:
3.1 Non-Australian Tea Tree Oils. In the last few years tea tree oil from Melaleuca alternifolia has been successfully cultured in more diverse locations such as Zimbabwe, Kenya, Vietnam, India, Guatemala and China – a fact often given little credit by the oil trade (Burfield 2001). Where acknowledged, the quality of these oils, especially the terpinen-4-ol chemotype, is often unfairly dismissed as inferior by Australian trade commentators (e.g. Fergeus 2000, writing of the Chinese sourced oil, and Bax 2005, referring to Indonesian oils) – however, the fact is, that the quality from some suppliers can be close to, or the equivalent of, the Australian oil, besides being considerably cheaper, especially that sourced from China.
China now supplies some 10% of the world production of tea tree oil, which is generally blended with Australian tea tree oil by oil-traders further down the distribution chain in order to gain a competitive advantage. Therefore the influence of Chinese tea tree oils on commercially available tea tree oils with respect to their composition and quality is more important than hitherto has been acknowledged. Further, interesting qualities are starting to emerge from China: an analysis of Tea Tree oil 60 (60% terpinen-4-ol content as opposed to oils of say 38-42% average Australian quality) is presented in the full forthcoming Cropwatch critique of the SCCP Opinion on Tea Tree Oil. The 60% oil was sold at an equivalent price to standard Australian oil of lower terpinen-4-ol content in early 2005. It is understood by Cropwatch that Chinese authorities intend to increase the cultivation of Tea tree plants in future, because of their beneficial soil-binding properties at a time when increased rainfall and flooding cause immense problems in parts of China.
Whilst the ATTIA have suggested in their letter of 14 Aug 05 to the SCCP that the characterisation and standardisation of tea tree oil should be a part of their on-going investigation, Cropwatch would maintain that commercial Australian (largely clonally produced) tea tree oils conforming to ISO 4730 (2004) cannot be the only ultimately available choice to EU tea tree oil users. In the real world, both harvested and wild-gathered organic tea tree oils, which include various strains and chemotypes, are all sold in the essential oil marketplace. In particular, because of the animal testing record of certain organisations representing Australian oil producers, not all tea tree oil customers (including aromatherapists) who are morally opposed to animal testing feel able to support Australian-sourced tea tree oils. Therefore in a marketplace allowing free consumer choice and preference, other geographically-sourced tea tree oils have to be considered.
It may be that other chemotypes of tea tree oil, such as the terpinolene chemotype, believed to be sporadically available from certain African and Chinese sources, are causing dermal problems to end-users. But the present research programme presented by the ATTIA which includes funding contribution by the Australian Government, is unlikely to specifically identify the root cause of alleged adverse skin problems of different chemotypes of tea tree oil, but merely promote Australia’s national economic interest in gaining SCCP approval for a clonally produced and standardised terpinen-4-ol chemotyped Australian tea tree oil product.
It has been suggested that since it can be proven that tea tree has a traditional medicinal use in Europe stretching over 30 years, then legally there can be a challenge for a need to establish any toxicological investigation for the use of tea tree in cosmetics. Further, there are some 700-odd further aromatic raw materials which have a history of use in fragrances, aromatherapy and herbal medicine, which are much less investigated than tea tree, and which don’t necessarily have a trade association to defend them. It is very much hoped that the privileged economic position in which the ATTIA finds itself in being able to investigate/research tea tree oil toxicology will not be taken as a blueprint for the further toxicological investigation of other oils with alleged instability & sensitising properties.
3.2 The compositional factors in sensitisation; the frequency of sensitisation to tea tree oil.
Previous published views on dermal effects of tea tree oil such as this one: “…were mild and transient. They mainly consist of allergic reactions.” (Ernst & Huntley 2000), have emphasised the somewhat benign nature of tea tree oil. Occasional cases of apparent sensitisation have been ascribed to several possible causes, such as artefacts from the oxidation of tea tree under poor conditions of storage, including peroxides, epoxides and endo-peroxides (Hausen 1999 – see below). However a full account of all the aging effects which occur in tea tree oil, including polymerisation and resinification, has yet to be established.
Williams & Home (1988) observe that the major part of the sesquiterpene content of tea tree oil is contained in the final 10% of the oil distilled, which requires as much time and energy to collect as the first 90%. In the above paper the authors discuss whether this content should be left in the biomass, but they suggested at the time that a decision was dependent on further investigation of cost and any biocidal (or other) properties. Holistic aromatherapists and other CAM oil customers, who of course, have traditionally required “complete oils”, are largely unaware of this situation, and it is conceivable that some small organic tea tree oil distillers may produce oils higher in sesquiterpene contents than more energy-conscious larger concerns with modern stills. This topic needs to be investigated further.
Rubel et al. (1998) considered that sesquiterpenes and their derivatives as the causative agents of sensitization in the case of three patients who tested strongly positive in patch testing to tea tree oil out of twenty-eight normal volunteers. Hausen et al. (1999) note that incomplete distillation of tea tree oil will enhance the concentration of terpinen-4-ol (not only, surely?) at the expense of the (allergenic?) sesquiterpene content, broadly in line with the opinion of Williams & Home above. The fate of several sesquiterpenoid components in tea tree oil is noted to decrease on storage but degradation products & routes have not been identified, possibly largely due shortcomings in commercially available Mass Spec. library databases for identification of likely intermediates and end-products of degradation processes for sesquiterpenoids in tea tree oil as normally carried out by GC-MS.
3.3 Adverse Skin Reactions from Tea Tree Oil.
The SCCP Opinion lists a number of published studies on Tea Tree oil without individual comments on either the scientific rigour of the work, or the reliability of the data and conclusions, as if an “index of concern” is proportional to the number of published papers on the subject. In a key paper not included in the SCCP literature search, Aspres & Freeman (2003) note that increased tea tree oil use has been linked with an increase in adverse reactions (mainly of allergic contact dermatitis) but point out that these conclusions are a result of individual case studies rather than investigations of the true risk of developing cutaneous reactions from application of the oil.
Looking at this paper in more depth, Aspres & Freeman (2003) tested 311 normal subjects with tea tree oil at 5,25 and 100% concentrations under occlusive patch testing. They conclude that topical application of tea tree oil is associated with negligible skin irritancy and that the risk of developing an allergic dermatitis from topical tea tree oil usage was less than 1%. Even the application of neat oil had resulted in a low irritancy score.
Another study (this time mentioned in the SCCP Opinion) involving a larger number of subjects was carried out by Pirker et al. (2003), who carried out a multicentre study in Germany & Austria using 5% tea tree oil dissolved in diethyl phthalate applied to dermatological patients and found 36 out of 3375 patients (1.1%) responded adversely overall. Regional responses ranging from 0% reaction (Berlin, Vienna) to 2.3% (Dortmund) could not be explained by the authors – but there again no analytical data and no peroxide values for substances used were stated in the work. This is not the first occasion in which regional variations in dermatological testing have been noted, and we need to know if the experimental design of these studies is reliable enough to justify the actual publications of the data, or whether non-uniform procedural steps are to blame, before concluding that the dermatological responses of regional human populations genuinely differ for physiological biochemical reasons so far not clearly identified.
Fritz et al. (2001) in another larger study listed by the SCCP had earlier reported on 1216 dermatology patients patch tested with tea tree which yielded seven cases (0.57%) of allergic contact dermatitis to tea tree oil, two exhibiting type IV sensitivity to fragrance mix or colophony suggesting cross reaction or turpentine contamination of colophony. This is not a remarkable result, suggesting that adverse reactions to tea tree oil in the population samples are quite minor even amongst dermatology patients.
Some published studies on tea tree oil need careful interpretation. For example Hausen et al. (1999) draws a parallel between with turpentine contact allergy and tea tree oil dermatitis, from tea tree oil that has been stored badly. The authors investigated the degradation products of the monoterpenes of tea tree oil as being the possible sensitizing agent and purchased a number of nature identical synthetic fragrance chemicals for epicutaneous elucidation in tea tree oil-sensitized guinea pigs. The team found that tea tree oil was a very weak sensitiser, and oxidized tea tree oil was 3 times more potent. The synthetic chemicals used to elucidate sensitizing agents in the above study will, of course, posses unnatural impurities and may present a different mix of isomers to those substances naturally occurring in tea tree oil, which they are attempting to emulate. Puzzlingly the same author (Hausen 1989) had already noted that “impurities in the tested materials in these sorts of studies are often mistaken for the causative agent of allergenicity” – but here in the 1999 study takes part in an experiment that essentially repeats this previous basic criticism of the experimental design! A far better plan would have been to isolate the individual pure natural components from the oil by spinning-band (adiabatic) distillation, preparative GC or similar process giving ultra-high purity isolates from essential oils – not to use synthetic imitations of naturally occurring chemicals. Further, the intra-dermal use of Freunds Complete Adjuvant although increasing the sensitivity of the test, also increases the stress to guinea pigs. Many “new age” users of tea tree oil will find this type of animal testing morally reprehensible.
Analysis of tea tree oils from 1-4 years old stored at ambient temperature (Burfield, unpublished data) revealed few oils with a peroxide value of more than 2.5; most considerably less. It is evident that the oils have oxidized in this period, from raised para-cymene levels, but it is difficult to make a case that tea tree oil is any less stable than other essential oils – for example than Mexican lime oil (Citrus aurantifolia), where the para-cymene level will also increase with time from oxidation of monoterpene hydrocarbons.
Considering the low incidence of contact allergy (typically 1% or less) which occurs in many of these studies mainly carried out on individuals with existing skin diseases, it is difficult to agree with the SCCP Opinion, that tea tree oil is unstable and unsafe.
3.4 Special investigations. The SCCP Opinion lists the work of Villar & Knight (1994) on the toxicology of topically applied tea tree oil to cats and dogs, but fails to identify why this information does not directly relate to humans.
3.5 Anti-mutagenic activity. Evandri et al. (2005) investigated both lavender and tea tree oils for mutagenic and antimutagenic activities by the bacterial reverse mutation assay in Salmonella typhimurium TA98 and TA100 strains and in Escherichia coli WP2 uvrA strain, with and without an extrinsic metabolic activation system. Neither essential oil had mutagenic activity on the two tested Salmonella strains or on E. coli, with or without the metabolic activation system.
By contrast with the SCCP approach to toxicity matters relating to natural aromatic products, COLIPA (the European Cosmetics Toiletry & Perfumery Association) in a paper dated 5th July 2005 entitled "Commission Proposal for a Revised Regulation on Chemicals (REACH): COLIPA Position on the Status of Substances derived from Botanicals" has taken the view that the REACH legislation is not adapted to natural ingredients of botanical origin - such as essential oils - (due to variability of composition resulting in the assessment of potential risks for health/environment requiring a methodology which would be beyond the reach of small producing farmers and small industry (incl. cosmetics companies)). The unworkability of REACH to these natural substances had previously been confirmed by the SPORT exercise, an initiative carried out by the European Commission and National Authorities with the participation of industry, including the cosmetic industry.
It would appear therefore that the SCCP needs to harmonise its approach on essential oils and natural aromatic products with the COLIPA approach, and consider the potential social and commercial damage of their policies to those employed in the essential oil producing trade. Previously the SCCNFP in a separate Opinion on the infamous 26 allergens issue*, in their published musings “did not consider that the production of essential oils would be threatened”, although of course, they had no actual expertise in the commercial arena to predict this outcome. In fact the oil trade and the craft of perfumery has since been irreparably damaged by the out-fall from this Opinion, which itself was based on dermatology data of poor scientific rigour (Burfield 2005).
N.B. *The SCCNFP (2002) resulted in a published Opinion on (alleged) fragrance allergens (SCCNFP/0392/00) which has been widely criticised and regarded as scientifically unsafe. The unfortunate incorporation of this Opinion eventually led to the 2003/15/EC Directive (7th Amendment) into the Cosmetic Products (Safety) Regulations 2004.
As indicated above, a full critique of the SCCP Opinion is in preparation, which is expected to show that the experience of end-users is that the use of diluted tea tree oil is safe, and the use of the neat oil in emergencies may be of more benefit that risk. The question of stability has to be seen in context with other essential oils, but if stored and used according to manufacturers recommendations, it is satisfactory. Doubts about incompleteness of safety data are also applicable to other essential oils, and anyway should not apply to natural products of botanical origin following the COLIPA and SPORT positions on this topic.
(on behalf of Cropwatch).
Aspres N & Freeman S (2003) “Predictive Testing for Irritancy and Allergenicity of Tea Tree Oil in Normal Human Subjects” Exog Dermatol 2,258-261”
Bax (2005) “Letter to the editor: Tea tree oil is safe” The Independent on Sunday (London, England); 1/16/2005
Burfield T. (2001) Natural Aromatic Materials – Odours and Origins Pub AIA Tampa.
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