Skin sensitisation elicitation: Evaluation of the general threshold and considerations for use

Allergic contact dermatitis (ACD) is an immune response to chemical haptens, involving induction and elicitation phases. Quantitative risk assessment (QRA) reviewing the skin sensitisation potential for all ingredients and using chemical-specific induction thresholds for skin allergens remains the current best approach for the safety evaluation of consumer products. However, elicitation thresholds have utility in secondary protection for pre-sensitised consumers.

The objectives were to (1) review the current elicitation threshold database, (2) evaluate whether predicted relationships between chemical induction and elicitation potencies enable elicitation threshold prediction and (3) discuss elicitation threshold utility as a secondary method of consumer protection.

In total, 28 publications (with 39 elicitation datasets) were included in non-linear regression analysis to derive elicitation thresholds for 22 allergens, including fragrances, preservatives and metals.

The median elicitation threshold (ED₁₀) for the expanded database was 0.95 μg/cm², which supports previously published general elicitation thresholds. The derived ED₁₀ for each chemical had only weak to moderate correlation with corresponding induction thresholds, thus limiting suitability as the predictive model.

Assessment of current EU fragrance allergen labelling and sensitiser labelling under the globally harmonised system in the context of general and chemical-specific elicitation thresholds shows that current practices are health protective.