Mapping of Former Strategies and Future Needs for Regulatory Prevention of Skin Sensitization: Cosmetic Products.

Contact allergy related to use of cosmetic products remains a considerable problem in the European Union population. The objectives of this study were to identify pitfalls in EU risk assessment methodologies and regulation(s) for cosmetic products and identify areas of potential improvements in future regulatory strategies. Two significant contact allergens, methylisothiazolinone and hydroxyisohexyl 3-cyclohexene carboxaldehyde, were investigated as examples. Other contact allergens were used to provide additional context. Opinions from the European Commission's scientific committees and regulatory documents were analysed to identify methodologies, processes and results in terms of preventive effects. The analysis revealed key observations in five areas: risk assessment methodologies, prediction approaches, key data, regulatory process and linkages. The case study indicated that reliance on predictive sensitization data from healthy volunteers generated unrealistically high no/low effect levels, while epidemiological surveillance and patient-based threshold data ultimately proved decisive, informing EU restrictions that led to declining sensitization rates. Read across approaches and chemical alert analyses show potential for earlier prevention, but their application has been inconsistent. Quantitative risk assessment remains limited by unresolved issues such as safety factors, aggregate exposure, and mixture effects. Strengthening transparency, integrating clinical evidence earlier, and improving regulatory coordination are essential to prevent future sensitization epidemics.