Fragrances are common causes of contact allergy. Geraniol (trans-3,7-dimethyl-2,6-octadiene-1-ol) is an important fragrance terpene. It is considered a weak contact allergen and is used for fragrance allergy screening among consecutive dermatitis patients. Analogous to other monoterpenes studied, such as limonene and linalool, geraniol has the potential to autoxidize on air exposure and form highly allergenic compounds. The aim of the present study was to investigate and propose a mechanism for the autoxidation of geraniol at room temperature. To investigate whether allergenic compounds are formed, the sensitizing potency of geraniol itself, air-exposed geraniol, and its oxidation products was determined using the local lymph node assay in mice. The results obtained show that the allylic alcohol geraniol follows an oxidation pattern different from those of linalool and limonene, which autoxidize forming hydroperoxides as the only primary oxidation products. The autoxidation of geraniol follows two paths, originating from allylic hydrogen abstraction near the two double bonds. From geraniol, hydrogen peroxide is primarily formed together with aldehydes geranial and neral from a hydroxyhydroperoxide. In addition, small amounts of a hydroperoxide are formed, analogous to the formation of the major linalool hydroperoxide. The autoxidation of geraniol greatly influenced the sensitizing effect of geraniol. The oxidized samples had moderate sensitizing capacity, quite different from that of pure geraniol. The hydroperoxide formed is believed to be the major contributor to allergenic activity, together with the aldehydes geranial and neral. On the basis of the present study and previous experience, we recommend that the possibility of autoxidation and the subsequent formation of contact allergenic oxidation products are considered in risk assessments performed on fragrance terpenes.

The non-professional use of UV-curing nail polishes poses a risk of sensitization from acrylates and methacrylates.

Background: Beeswax, both white and yellow, has many uses, such as in lip balm. This material can cause contact allergy, although not many cases have been described.Methods: Ninety-five patients with contact cheilitis, facial eczema or a suspicion of contact allergy to beeswax were patch tested with yellow and white beeswax and with propolis, in addition to the Swedish baseline series. Patients who reacted positively to beeswax were additionally tested with caffeic acid, and two derivatives thereof that are believed to be important haptens in propolis.Results: Seventeen patients had positive reactions to beeswax. Fourteen of these patients had been tested with both yellow and white beeswax. Among those 14, eight had positive reactions to both types of wax, five only to yellow wax, and one only to white wax. Of the 10 wax-positive patients tested with caffeic acid derivatives, three reacted positively.Fourteen beeswax-positive patients also had positive reactions to propolis.