Persistence of an allergen in hair after glyceryl monothioglycolate-containing permanent wave solutions

Glyceryl monothioglycolate, a reducing agent used in permanent waving solutions, is a recognized cause of allergic contact dermatitis. Because of an unexplained persistence of dermatitis in beauty shop clients after exposure to permanent wave solutions containing glyceryl monothioglycolate, we looked for the presence of this or a cross-reacting substance in permanent-waved hair as a possible source of continued exposure to the allergen. Seventeen subjects sensitive to glyceryl monothioglycolate underwent patch testing with hair samples collected before and at various times after a permanent wave containing glyceryl monothioglycolate. None reacted to hair that had not received a permanent, while 7 of 17 showed positive reactions to the permanent-waved hair. Positive reactions were seen in hair collected as long as 3 months after the permanent. This suggests that a glyceryl monothioglycolate-related allergen is retained in hair for up to 3 months after the permanent, which may explain the long-lasting dermatitis that occurs in clients sensitive to glyceryl monothioglycolate.