Sofa dermatitis: Value of patch test with 2-(thiocyanomethylthio)benzothiazole

In 2008, numerous cases of allergic contact dermatitis caused by leather chairs (sofa dermatitis) were reported, with dimethylfumarate being the culprit allergen. However, octylisothiazolinone, methylisothiazolinone and cobalt have also been associated with cases of sofa dermatitis. An antifungal agent, 2-(thiocyanomethylthio)benzothiazole (TCMTB), has also previously been described as a contact allergen in leather.

Seven patients were referred to the Department of Dermatology of the Cliniques universitaires Saint-Luc, Brussels, Belgium with suspicion of allergic contact dermatitis caused by leather sofas. They were patch tested with the European Baseline Series, additional series (according to the patients' history and clinical aspect of the eruption), dimethylfumarate (4/7 patients) and with TCMTB.

All seven patients presented a positive reaction to TCMTB and only one presented a concomitant positive reaction to dimethylfumarate. All patients showed clinical improvement after avoiding contact with their leather sofa.

2-(Thiocyanomethylthio)benzothiazole (TCMTB) is probably an underestimated allergen present in leather chairs (responsible for the so-called 'sofa dermatitis'), and more generally in leather objects. It is, therefore, important to test with TCMTB 0.1% petrolatum in case of contact dermatitis related with leather products.