P-214 Prevalence of Active Sensitization: About 565 Patients Tested From 2002 to 2023

Introduction Active sensitization is an extremely rare but dreaded complication of patch testing. It is an iatrogenic sensitization reaction to an allergen induced by the application of a patch test. The aim of this study was to assess the prevalence of active sensitization to patch tests over a twenty-two-year period. Methods This is a retrospective study of patients who underwent patch testing at the Dermato-allergology unit of the Occupational Medicine Department of the Fattouma Bourguiba Monastir University Hospital from 2002 to 2023. These patients were referred to the department on suspicion of allergic contact dermatitis. Results A total of 565 patients underwent patch testing. At least one allergen was found to be positive in 343 patients (60.7% of cases). Active sensitization was noted in six patients (a prevalence of 1.06%). The allergens involved were Thiuram Mix (2 cases), P-Phenylene Diamine (2 cases), Disperse Bleu 3 (2 cases) and Disperse Orange 3 (2 cases). Discussion Active sensitization is frequently caused by a single allergen and results in a positive result at the site tested after 10 to 21 days. Repetition of the test is the only valid argument for suggesting it, which becomes positive within 1 to 4 days. Active sensitization can only be avoided by referring to the right concentrations and the right test vehicles. Conclusion Active sensitization poses an ethical problem. It is therefore necessary to inform patients of the risks involved in this test and to obtain their written consent.