Targeted testing with diethylthiourea often reveals clinically relevant allergic contact dermatitis caused by neoprene rubber.

Diethylthiourea is widely used in the rubber industry, particularly in neoprene rubber, and may cause allergic contact dermatitis. However, as thiourea allergens are not part of the European baseline series, the diagnosis of allergic contact dermatitis caused by thiourea compounds depends on clinical suspicion and aimed testing. The aims of this study were to evaluate the occurrence of sensitization to diethylthiourea during a 19-year period by using data from the Allergen Bank database at the Department of Dermatology and Allergy Centre, Odense University Hospital, and to evaluate whether the yield of aimed patch tests with diethylthiourea differed between the dermatologists in practice and those working in the dermatology department. A total of 239 patients were patch tested with diethylthiourea 1% in petrolatum obtained from the Allergen Bank. The records for patients with positive reactions were evaluated retrospectively. One hundred and fifty-one patients were tested by 27 different dermatologists in private practice, and positive reactions were found in 16% (24/151) of the patients; 88 patients were tested at the dermatology department, and positive reactions were found in 15% (13/88). Thus, 15% (37/239) had positive patch test reactions to diethylthiourea, all with current clinical relevance and all strong. Clinical suspicion of neoprene rubber allergy and subsequent aimed patch testing with diethylthiourea give a high yield of clinically relevant allergic patch test reactions for both dermatologists in practice and dermatologists in the hospital department.