There are numerous species of lavender, the most well-known one is Lavandula angustifolia (known also as Lavandula officinalis). The majority of species contain essential oils in 1-3%. The oil is a mixture of different ingredients, may contain linalool, linalyl-acetate, camphor, geraniol, cumarins and flavones. Patients with geraniol sensitivity show a weak or strong reactions to ylang ylang oil or to lavender oil, thus they usually contain geraniol in various proportions. Cross-reactions of lavender oil have also been reported with Balsam of Peru and wood tar, but in case of a common presence simultaneous sensitization may also occur 12345.

Due to its therapeutic (relaxing, antidepressive, antimicrobial, antimycotic) effects, lavender oil has been used for centuries as an alternative drug for a long time. Its use in cosmetics and in foods is also very popular worldwide, Exposure can be airborne (aromatherapy, perfumes) by oral route (teas, honey, jam, sweets, spices) or direct skin and mucous membrane contact (soaps, body oils, creams and mouthwashes)1234567.

The increasing number of applications resulted hypersensitivity-reactions in various localisations. Lavender oil can provoke contact dermatitis and photoallergic reactions. The strong, concentration-dependent irritative effect of the constituents may also raise the development of hypersensitivity14678910.

The Contact Dermatitis Work-Group of the Hungarian Dermatological Society organised and conducted a multicentre survey to map the frequency of lavender hypersensitivity in Hungary.

We performed the epicutaneous patch tests in our multicentre, prospective study between February 1^st 2013 and February 1^st 2014. Besides environmental routine test series we also used 2% lavender oil in pet. (All test material from AllergEAZEBrial). The occlusion time by testing was 48h, the allergens were applied on the back. We used Curatest(Lohmann & Rauscher) chambers. Evaluation of the test was performed at the 60^th minute of the occlusion, then on D2, D3, D4 and D7. Reactions were taken as positive 1+ or more intense11.

Number of the consecutivetested patients was 1509, 350 men and 1159 women. The mean age was 46.7 years (range: 9-92 years).

The number of tested patients were: in Budapest 711 (Dept. of Dermatology, Venerology and Dermatooncology of Semmelweis University /605/ + Dermatological Outpatient Dept. of the Unified Szt. István- Szt. László Hospital /74/ + National Work Hygiene and Occupational Healthcare Institute /32/), in Szeged: 299 (Dept. of Dermatology and Allergology of the Szent-Györgyi Albert Clinical Centre), in Kaposvár: 209 (Somogy Megyei Kaposi Mór Teaching Hospital Dpt. Dermatology) in Debrecen: 195 (Dpt. of Dermatology of the University of Debrecen, in Miskolc: 95 (Semmelweis Medical Centre of Miskolc, Centre of Dermatology).

The most frequent clinical diagnoses of the patients (done before the patch testing) were allergic contact dermatitis (n=469), irritative contact dermatitis (n=476), atopic dermatitis (n=108) and seborrhoeic dermatitis / rosacea (n=150) (Table 1.).

We verified contact hypersensitivity to lavender oil in 8 patients (0.53%): we could not detect any immediate reaction, all the positivities were late-type reactions, most reactions were observed at or after D3 (Table 1, Table 2). In 7 cases the present relevant positivity was confirmed by a specific provoking factor, one patient could not identify actually the contact (patient 1.: unknown relevance). Clinical symptoms affected the face and the eyelids in 5 patients.

We found associated sensitization in four patients (formaldehyde, mercury chloride, nickel, propylene glycol, 2-mercaptobenzothiazole /MBT/, thiuram mix, mercury chloride - ammoniated). We did not find any Fragrance Mix, Fragrance mix II, Balsam Peru (Myroxylon pereirae), colophonium, wood tar mix, sesquiterpene lactone mix, or turpentine peroxides hypersensitivity among our patients with lavender oil sensitivity (Table 2.).

The skin symptom-provoking contacts were cosmetics (soap, baths, shampoos, creams) air fresheners, volatile oil and the lavender plant itself. One of our patients, a 55 year old woman came to our clinic with hand dermatitis (after direct contact with lavender plant) (Figure 1.). Besides this results, we detected 8 irritiant reactions.

Exposure to lavender oil can induce contact dermatitis or photoallergic reactions. The strong concentration-dependent cytotoxic effect of its constituents may cause irritation and also enhance sensitisation. This may typically occur during application of different mixtures of volatile oils, tinctures, massage oils, perfumes and aromatherapy. Linalool and linalyl acetate are week sensitisers but in case of getting into contact with air, autooxidation leads to formation of oxidation products and thus they become strong allergens1213. Its photosensitizing reactions are thought to be associated with cytotoxicity and psoralen contamination of the essential oils2. In the course of distillation of lavender flower other allergenic components can also be identified: lavandulol, 1,8-cineol, lavandulyl acetate, camphor and geranium oil. Lavender oil is also often applied on the skin without dilution and it appears in the plasma due to the rapid absorption of its ingredients 31415.

Lavender oil is usually patch tested at 2% in pet, but De Groot recommends different concentrations (1,2,5,8,10,16 % pet ) – for various species of the plant1617. Recent results of a French centre suggest to include lavender oil testing in the baseline series18.

Searching the frequency of contact sensitization to lavender, Calnan19 detected a prevalence of 0.52% in 1970. Rudzki proved lavender contact sensitization with 2% lavender oil in pet. in 2% of 200 patch tested patients20. Larsen et al verified a lavender sensitization rate of 2.8% by testing selected fragrance - sensitive patients16.

In a Japanese study conducted between 1990 and 1997, Sugiura et al found an increasing frequency (1.1% - 13.9%) of contact allegy to lavender oil tested at 20% pet, in a selected population of patients with cosmetic contact dermatitis, with lesions localized mainly to the face, eyelid and hands. Dermatitis was related to exposure to air fresheners, perfumes, aroma candles and the plant itself 21. In ours as in other studies, anatomical localisations of typical lavender contact allergy are hands, body, face2489152223, but exposure to the allergen frequently remains hidden21.

According to the data of our multicentre study the prevalence of sensitization to lavender oil in Hungary is 0.53% at present (8/1509 patients). In the course of the tests we could not detect any immediate test-reaction, all the positivities were late-type test-reactions. In 7/8 cases the present relevant positivity was confirmed by a specific provoking factor, typical were cosmetics, air fresheners and the plant itself. According to our everyday practical experiences a lot of people use lavender oil in cosmetics, in foods or as natural drug in our country. The contacts become more and more frequently, so further increase of the sensitivity rate may be expected.

The work has been approved by the ethical committees and all the subjects gave informed consent to the work.