Non-Allergic Contact Dermatitis in Different Professions: The Analysis in the Triveneto Region (Northeast of Italy) Patch Test Database from 1997 to 2023

Contact dermatitis (CD) is one of the most common occupational skin diseases worldwide, and patch tests are used to identify allergic contact dermatitis (ACD). Half of the cases were negative for patch tests (non-ACD). In our study, we aim to analyze patch test negativity in different occupational groups from the Triveneto (northeast Italy) Patch Test Database and to identify associated demographic and exposure-related factors. Data from 31,948 patients evaluated for suspected ACD between 1997 and 2023 were analyzed. All participants underwent clinical examination, completed a standardized questionnaire, and underwent patch testing. Occupational categories and anatomical sites were aggregated into broader groups and analyzed with multivariable logistic regression models. Among 31,948 patients with CD, 43.4% had negative patch test results. The mean age was 43.8 ± 17.2 years, with a predominance of female patients (66.7%). Hands were the most affected body site (30.9%), with lower prevalence of patch test negativity (OR 0.936; 95% CI 0.892–0.981). Non-ACD was more frequent among non-workers as students (OR 1.380; 95% CI 1.192–1.597) and in occupational groups involved in wet work, detergent use, mechanical friction, and exposure to irritating substances such as mechanics (OR 1.152; 95%CI 1.018–1.204) and cooks with hand dermatitis (OR 1.784; 95%CI 1.936–3.071). These findings highlight the importance of non-ACD, the need for better prevention strategies, improved skin protection practices, and early recognition of irritant exposure in the workplace.