Air-oxidized linalool-a frequent cause of fragrance contact allergy

Background. Linalool is a common fragrance terpene that, in pure form, is not allergenic or is a very weak allergen. However, linalool autoxidizes on air exposure, and the oxidation products can cause contact allergy. In a Swedish study, oxidized linalool 6.0% in petrolatum (pet.) gave 5% positive patch test reactions in 2500 dermatitis patients. Objectives. To investigate whether oxidized linalool 6%, with a stable concentration of the main haptens, the linalool hydroperoxides (Lin-OOHs) in pet., could be a useful tool for the detection of contact allergy in an international setting. Methods. Oxidized linalool 6.0% (Lin-OOHs 1%) pet. was tested in 2900 consecutive dermatitis patients in Denmark, the United Kingdom, Singapore, Spain, Sweden, and Australia. Results. Overall, 6.9% (range 313%) of the patients showed positive patch test reactions to oxidized linalool. Doubtful reactions were found in 9.2% of the patients (range 036%). Few irritant reactions were seen. Conclusions. In an international setting, oxidized linalool has been shown to be a common allergen. Oxidized linalool 6.0% (Lin-OOHs 1%) pet. is a useful, standardized and stable tool for the detection of contact allergy in dermatitis patients. Many patients showing positive patch test reactions to oxidized linalool would not have been informed of their fragrance allergy if this specific test had not been performed.