Contact allergy to fragrances with a focus on oak moss absolute

Abstract: The exposure to fragrances is widespread and contact allergy to fragrance substances affects 1–4% of the general population. Many fragrance substances are volatile and it can therefore be suspected that they may evaporate from petrolatum patch test preparations applied in test chambers. In the first two papers included in this thesis the aims were to i) to investigate the stability of fragrance preparations in petrolatum when applied in patch test chambers, and ii) to investigate the patch test reactivity to samples of fragrance mix I (FM I) and fragrance mix II (FM II) when applied in test cambers 6 days in advance or immediately before the patch test occasion. Oak moss absolute (OMA), an extract derived from the lichen Evernia prunastri, is a common cause of fragrance contact allergy. OMA contains several allergens, among them atranol and chloroatranol, which have been found to be strong allergens in humans. Therefore, the fragrance industry nowadays provides treated OMAs, where the content of atranol and chloroatranol has been reduced. The aims of studies III and IV in the thesis were to iii) compare the eliciting capacity of treated and untreated OMA samples in patch tests with dilution series and in repeated open application tests (ROATs), and iv) to investigate the reaction pattern in OMA-allergic subjects patch-tested with thin-layer chromatography (TLC) strips of treated and untreated OMA samples. The findings were as follows: i) The concentrations of 4 of 7 substances investigated decreased by ≥20% within 8 h when stored in Finn chambers at room temperature. The decrease in concentration was slower when the test preparations were stored in a refrigerator. Statistically significantly more reactions were observed for the freshly applied sample of FM I than to the pre-loaded sample, demonstrating that FM I patch test prepared in advance may give false-negative reactions. No corresponding difference was observed for FM II. This is likely explained by differences in volatilities between the ingredients of FM I and FM II. iii) OMA-allergic subjects were statistically significantly less patch test reactive to the treated OMA sample than to the untreated sample. No significant difference was observed in the ROAT, though there was a significant difference in the time required to elicit a positive reaction. iv) The TLC patch tests indicate the presence of sensitisers other than atranol and chloroatranol in the untreated OMA sample. The studies on OMA indicate that the residual levels of atranol and chloroatranol and/or the presence of other sensitisers in the treated OMA samples may elicit allergic reactions in previously sensitised individuals.