Scalp Dermatitis in Patients Sensitized to Components of Hair Products

Para-phenylenediamine (PPD) is the most common allergen in patients with scalp dermatitis. The rate of PPD sensitization is higher in nonwhite compared with white patients. In the small number of patients with isolated scalp involvement, positive patch tests to PPD were documented in a minority. Other allergens found in hair products may present without scalp symptoms. Patients with dermatitis affecting areas other than the scalp should provide their hair product ingredients to guide patch test selection.