Stratum corneum levels of inflammatory mediators and natural moisturizing factor in patch test reactions to thiurams and fragrances and their possible role in discrimination between irritant and allergic reactions to hapten mixtures

Background Patch test (PT) reactions to thiuram mix (TM) and fragrance mix (FM) I or II without concomitant reactions to their single constituents are potentially caused by the irritant properties of the mixes. Objective Comparing inflammatory profiles of PT reactions to TM, FM I, FM II, and their constituents and assessing their potential in discrimination of irritant and allergic reactions. Patients and Methods Levels of 14 cytokines and natural moisturizing factor (NMF) were determined in stratum corneum samples collected from PT reactions to TM, FM I or II, their constituents, and petrolatum (pet.) control sites in 36 individuals. Results Levels of interleukin (IL)‐16, chemokine (CXC motif) ligand (CXCL) 8, CXCL10, chemokine (CC motif) ligand (CCL) 17, and CCL22 were significantly increased in reactions (+, ++) to thiurams and fragrances compared to their petrolatum. controls, except for PT reactions to FM I/II with negative breakdown testing in which, however, decreased levels of NMF were observed. In doubtful reactions to FM I/II with negative breakdown testing, NMF was significantly lower than in petrolatum controls. Conclusions PT reactions to thiurams and fragrances indicate a Th2‐skewed inflammation. The inflammatory profiles suggest that weak or doubtful FM I/II reactions without accompanying reaction to a constituent were irritant. IL‐16 might be suitable to distinguish irritant from allergic reaction.