FS06.2 Autoxidation of linalool and impact on the sensitizing capacity and allergenicity

Linalool is one of the most frequently used fragrance chemicals in scented products and a large population is exposed to it. It is therefore important to study the allergenic properties of linalool, and the effect of autoxidation. Objectives: To study the autoxidation of linalool and identify formed oxidation products, to investigate the impact of autoxidation on the sensitizing capacity and to study the frequency of contact allergy to oxidized linalool among consecutive dermatitis patients. Methods: Linalool was air‐exposed and the degradation followed with GC. Oxidation products were identified with GC‐MS and NMR. Pure linalool, 2 different states of oxidized linalool and 3 oxidation products were tested for their sensitizing capacity in the local lymph node assay (LLNA). Consecutive dermatitis patients were patch‐tested with oxidized linalool and a fraction of oxidized linalool. Results: Linalool started to decompose immediately when air‐exposed. Several oxidation products were identified among which 3 (2 hydroperoxides and an alpha, beta‐unsaturated aldehyde) contain structural features that make them potential allergens. LLNA showed that the 3 oxidation products were moderate allergens, and that the sensitizing potential of linalool increased with longer air‐exposure times. In the patch‐test study positive reactions were observed to oxidized linalool in 1.65% of the patients. Conclusions: The extensively used fragrance chemical linalool is not allergenic in itself. The autoxidation process that takes place at air‐exposure leads to the formation of sensitizing oxidation products. The frequency of consecutive patients reacting to oxidized linalool shows that the experimental findings are clinically important.