Stratum Corneum Biomarkers for Differentiating Irritant and Allergic Contact Dermatitis

Background/Objectives Occupational hand dermatitis (HD) comprises irritant and allergic contact dermatitis (ICD and ACD), which share clinical features, often overlap, and may coexist with atopic dermatitis (AD), complicating diagnosis. The objective of this study is to explore whether stratum corneum (SC) biomarkers discriminate ICD from ACD. Patients We recruited 126 patients from the Occupational Dermato‐allergology Clinics of the Amsterdam UMC. Methods SC samples were collected from lesional HD skin and patch test reactions to nickel, chromium, methylisothiazolinone, sodium lauryl sulfate (irritant), and control sites. Thirty‐three biomarkers were analyzed. Random forest and penalized regression models were trained on the patch test dataset and validated in HD; an additional model was trained and validated in HD. Exploratory analyses evaluated discrimination among individual allergens and between AD, ICD and ACD. Results The patch test model showed good discrimination between ICD and ACD (mean AUC 0.85, 95% CI 0.82–0.87), driven primarily by skin barrier–related biomarkers. In HD, performance declined (mean AUC 0.51, 95% CI 0.26–0.76); sensitivity for ACD was 88%. Model trained and validated within HD achieved mean AUC of 0.60 (95% CI 0.57–0.64). Discrimination between individual allergens yielded mean AUC of 0.75 (95% CI 0.72–0.77). Conclusion SC biomarkers discriminated ICD from ACD good in acute patch test, but showed limited discrimination in HD, reflecting differences between acute and chronic inflammation.