Allergic contact dermatitis caused by dialkyl thioureas in a patient with sleep apnea

Allergic contact dermatitis of the scalp is relatively uncommon. This is a case report of a patient with chronic scalp dermatitis in the distribution of his continuous positive airway pressure (CPAP) mask neoprene rubber strap. Our objective was to identify any relevant contact allergens. Patch testing to the North American Contact Dermatitis Group (NACDG) Standard Allergens, a series of supplemental rubber allergens, and a sample of the neoprene from the patient's mask strap was performed. Relevant allergies to dialkyl thioureas, and the neoprene rubber portion of the CPAP mask strap were identified. Replacement with a cloth strap resulted in clearing of the dermatitis.