Sensitization to thiourea derivatives among Finnish patients with suspected contact dermatitis

Abstract

Thiourea derivatives in rubber products may induce contact sensitization and allergic contact dermatitis. Sensitization is most often from neoprene rubber, but the multitude of possible sensitizing products has remained poorly characterized. The aim of this study was to collect information on the occurrence of thiourea-related contact allergy and to show novel sources of sensitization. A mixture of dibutyl-, diethyl-, and diphenylthiourea was included in patch test baseline series in five Finnish dermatology clinics during 2002-2007. In addition, an extended series of rubber chemicals was tested in patients with suspected rubber allergy. Sources of sensitization to thioureas were analysed in sensitized patients. Thiourea mix yielded positive patch test reactions in 59 of 15,100 patients (0.39%); 33/59 patients were also tested with individual rubber chemicals. Diethylthiourea was positive in 24/33, diphenylthiourea in 5, and dibutylthiourea in 1 patient. The most common sources of sensitization included various neoprene-containing orthopaedic braces, sports equipment, and foot wear. The sources of sensitization to thiourea chemicals were detected in most cases. These sources comprise a heterogenous group of products extending from orthopaedic materials to sports equipment.