Should Hydroxyisohexyl 3-Cyclohexene Carboxaldehyde (Lyral®) still be part of the Baseline Series?

Abstract

Background and objectives: Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC), or Lyral®, is a fragrance marker that is part of the Fragrance Mix II (FM II) and is still patched as an independent allergen within the European and other baseline series despite the European Commission banning its use in cosmetics in 2021. We aimed to study the prevalence of sensitization to the HICC in Spain and its simultaneous positivity with the FM II to determine whether it should be part of the Spanish baseline series.

Material and method: We analysed all consecutive patients simultaneously patch-tested with HICC and FM II within the Spanish Contact Dermatitis Registry (REIDAC) from June 1^st, 2018 through December 31^st, 2023.

Results: A total of 96 (0.8%) out of 12,029 patients analysed yielded positive to HICC and 396 (3.3%) to FM II. In 53% and 64% of the patients, respectively, findings were considered currently relevant. A total of 72 out of 96 (75%) HICC positives would be detected if only FM II was patched.

Conclusions: Prevalence of HICC sensitization in Spain is low and has decreased in recent years. HICC is a prohibited fragrance in cosmetics and FM II detects 3 in 4 sensitized patients. Our results suggest that HICC should remain outside the Spanish baseline series and support its exclusion from the European baseline series.