Chemical Mixture Exposures and Their Effects on Sensitisation and Elicitation Responses: A Systematic Review

Consumers and workers are generally exposed to multiple allergens and irritants simultaneously in products. This systematic review of 13 studies: 4 clinical, 6 animal, and 3 in vitro studies, suggests that co-exposure often enhances both sensitisation and elicitation reactions. When an irritant is combined with an allergen, the threshold for sensitisation and elicitation is lowered, and the severity of reactions is increased. Animal models suggest that weak allergens, when combined, can elicit responses at individual subthreshold doses, supporting their role as immune-enhancing adjuvants. Current regulations generally assess allergens or irritants in isolation, potentially overlooking the combined effects of low-level exposures from everyday products. There is a need to refine safety standards and ensure that risk assessment tools reflect real-world interactions between multiple allergens and irritants. Contact allergy is frequent and increasing in the population. A clearer understanding of mixture effects in sensitisation and elicitation responses is essential to protect the general population from developing contact allergy.