Please be very careful when recommending the use of essential oils, as they are well documented as sensitizers for contact allergic dermatitis. As a podiatrist with a special interest in dermatology, I feel an obligation to try to explain to patients and practitioners why we are no longer recommending TTO (Tea Tree Oil) or LO (Lavender Oil).

First and foremost the safety of use of TTO in practice has been raised by many bodies, such as the Federal Institute for Risk Assessment (see here: http://www.bfr.bund.de/cm/349/use_of_undiluted_tea_tree_oil_as_a_cosmetic.pdf)

Taken from the above document: "Concentrated tea-tree oil has been classified as harmful according to the self-classification of the International Fragrance Association (IFRA) and is labelled with R-phrases R 22 (harmful if swallowed) R 38 (irritating to skin) and R 65 (may cause lung damage if swallowed) as well as the symbol Xn (harmful) (IFRA Labelling Manual 1, 2001). These indications of health hazards are also part of the safety data sheets of raw material suppliers....."

The EU Scientific Committee also expressed serious concerns about the safety of TTO in products, back in 2004 (see the strongly worded report here: http://ec.europa.eu/health/ph_risk/committees/04_sccp/docs/sccp_o_00c.pdf)

The above is a rather lengthy document, but the conclusion reads:

"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, enotoxicity/carcinogenicity and reproductive toxicity."

Put simply, the EU stated that `even small amounts of the undiluted oil could be unsafe and unstable after clinical trials found users risked rashes and allergies as it is a severe irritant to the skin and degraded rapidly if exposed to air, light and heat`.

The active component in Lavender Oil is Linalool, which is a terpenoid. Amongst the active ingredients in TTO are the terpenoids; terpinolene, ascardiol and a-terpinene. These are thought to be responsible for the much publicised `antimicrobial activity of both LO and TTO`. However, the majority of trials quoted in favour of the antiseptic and antifungal effects of TTO have been carried out in vitro. The clinical in vivo trials often revealed it to be no better than placebo. No clinical studies have revealed superiority of TTO or LO over existing licensed pharmacological treatments for bacterial skin infections .

Regardless of the unproven efficacy of TTO and LO, my greatest concern is that practitioners are continuing to recommend the use of TTO and LO without first explaining the risks, i.e. the nature of oxidation. In both LO and TTO the oxidation process of the terpenoids leads to the formation of peroxides, epoxides and endoperoxides. The potency of these to act as triggers for contact allergy increases with oxidation of the oil upon exposure to light, moisture, heat and air. So much so that, when oxidated both oils have a sensitizing capacity multiple times stronger than a newly opened fresh bottle, after just a few days if opened daily, thus rendering the oils as severe irritants. Terpenoids have been documented as known sensitizer for allergic contact dermatitis for many years and the incidence of reactions to oxidized TTO is recorded by the EU as being relevant enough to warrant warnings on TTO products.

We often hear about the `natural antimicrobial` effects of TTO and LO in the media, which to the un-suspecting public equates to `safe`. Note what Frances Fewell, director of the Institute for Complementary Medicine states; “Because essential oils are natural products, the public often assumes they must be safe. You should never apply any sort of essential oil directly to the skin without diluting it first in a suitable carrier oil. Tea tree oil has become very popular, and many people have started applying it directly to deal with acne and skin infections. In fact this is a very aggressive oil. The skin can dry out, blister or form a rash.”

In addition to the associated risk of allergy, the New England Journal of Medicine published evidence that TTO has properties that can lead to gynaecomastia - the growth of breasts. The researchers stated that when boys stopped using the oils, the breasts disappeared. They, therefore, concluded that the repeated use of such oils may also disrupt hormonal function.

In summary, the unproven safety (and efficacy) and the increased incidence of contact dermatitis associated with use of topical neat TTO and LO in addition to the amount of patients that I have personally seen presenting with Paronychia , is enough for me to discourage their use, particularly in open wounds which are often associated with bacterial skin infections like impetigo, folliculitis, cellulitis.

Thanks very much. This is very useful.

I knew about the sensitising effects of neat Tea Tree and that essential oils are prone to oxidation, but I did not know that it becomes oxidised so easily in just a few days of opening the cap. I thought that the oil would have a better shelf life if stored in a cool place in a dark glass bottle, and out of sunlight, and would not deteriorate in just a few days if the cap is opened daily.

Do you have any reports/ references which relate to the sensitising effects of lavender oil too?

Note: have heard about therapists who use essential oils regularly suddenly developing a reaction to some oils like lavender. I have not heard about adverse effects of using lavender oil suitably diluted in a carrier oil, and regarded this as quite a "safe" oil if used properly diluted and applied only topically, and with antimicrobial properties and beneficial for a number of skin conditions).

Please note that I am not against the use of essential oils, if used appropriately. I will find further references relating to sensitivity as requested.

Schempp CM, Schopf E, Simon JC. [Plant-induced toxic and allergic dermatitis phytodermatitis)]. Hautarzt. 2002 Feb;53(2):93-7. German.

Sugiura M, Hayakawa R, Kato Y, Sugiura K, Hashimoto R. Results of patch testing with lavender oil in Japan. Contact Dermatitis. 2000 Sep;43(3):157-60.

Anderson C, Lis-Balchin M, Kirk-Smith M. Evaluation of massage with essential oils on childhood atopic eczema. Phytother Res. 2000 Sep;14(6):452-6

Varma S, Blackford S, Statham BN, Blackwell A. Combined contact allergy to tea tree oil and lavender oil complicating chronic vulvovaginitis. Contact Dermatitis. 2000 May;42(5):309-10.

Coulson IH, Khan AS. Facial 'pillow' dermatitis due to lavender oil allergy. Contact Dermatitis. 1999 Aug;41(2):111.

Schaller M, Korting HC. Allergic airborne contact dermatitis from essential oils used in aromatherapy. Clin Exp Dermatol. 1995 Mar;20(2):143-5.

Rademaker M. Allergic contact dermatitis from lavender fragrance in Difflam gel. Dermatitis. 1994 Jul;31(1):58-9.

Brandao FM. Occupational allergy to lavender oil. Contact Dermatitis. 1986 Oct;15(4):249-50.

Kim HM, Cho SH. Lavender oil inhibits immediate-type allergic reaction in mice and rats. J Pharm Pharmacol. 1999 Feb;51(2):221-6.

Benito M, Jorro G, Morales C, Pelaez A, Fernandez A. Labiatae allergy: systemic reactions due to ingestion of oregano and thyme. Ann Allergy Asthma Immunol. 1996 May;76(5):416-8.

Lovell CR.1993, Plants and the Skin, Blackwell, Oxford.

Mitchell JC, Rook A, 1979, Botanical Dermatology, Plants and Plant products injurious to the skin, Greengrass, Vancouver

I agree, so long as the essential oil is suitably diluted in a carrier oil and used under the direction of an experienced/qualified practitioner, then they may have some benefit for some skin conditions. However, as with all medicaments, it is important to highlight the potential risks.

Hope that helps.

Hi Belinda

Thank you so much. Your answer is very helpful to me. Thanks also for including all the references.

Aromatherapy may have its limitations, instead low dilutions may be more rewarding, esp jasmine, rose oil or even widely used eucalyptus oil etc.,