Contact allergy to farnesol in 2021 consecutively patch tested patients. Results of the IVDK.

Farnesol is one of the fragrances considered to be a significant contact allergen. Therefore, it was decided by the European Union to label products containing farnesol. Farnesol was tested [5% petrolatum (pet.)] together with the standard series between 1 January 2003 and 30 June 2003 in 2021 consecutive patients, 1243 females and 778 males. Of these, 22 [1.1%, 95% confidence interval (CI): 0.7-1.6%] had a positive reaction to farnesol. 147 (8.1%) of those 1825 tested to Myroxylon pereirae resin (balsam of Peru, 25% pet.) at the same time reacted positively, 143 (7.8%) of those 1823 tested to the fragrance mix (FM) (8% pet.) and 34 (1.9%) of 1831 tested to propolis (10% pet.). With regard to concomitant reactions in farnesol-positive patients, 5 of 22 reacted additionally to the FM [odds ratio (OR): 4.3; CI: 1.53-12.15] and 2 (of these 5) additionally to M. pereirae resin (OR: 1.27; CI: 0.29-5.54). The strongest association was seen to propolis (OR: 6.2; 95% CI: 1.4-27.7). Compared to those with negative reactions to farnesol, the group of patients allergic to farnesol was characterized by a higher proportion of young females and office workers, and the hand and the face were more often affected. In conclusion, farnesol is an important allergen. We recommend that farnesol should be included in a fragrance patch-test preparation and that its use should be regulated for consumer safety reasons. Furthermore, the extent of exposure to farnesol should be further studied.