[Allergic contact dermatitis of the scalp]

Contact allergy represents an important differential diagnosis to other skin diseases of the scalp. The typical efflorescences, spreading in the periphery, pruritus, and the clinical history support the differential diagnosis. Since the scalp is particularly resistant to contact dermatitis, allergens applied to this area often produce dermatitis of the eyelids, ears and neck. Nevertheless, potent allergens such as para-phenylendiamine can also cause severe reactions of the scalp. The most important allergens eliciting contact allergy of the scalp are found in bleaches and dyes, shampoos and conditioners, products for perm waves and straighteners as well as topical drugs. Besides active ingredients or drugs, vehicles and preservative agents represent additional allergens. The use of topical steroids and oral antihistamines usually results in rapid resolution of the dermatitis, systemic steroids are only necessary in severe cases. Epicutaneous patch testing on the basis of available series combined with the ingredients of the suspected elicitors confirms the diagnosis and facilitates allergen avoidance as well as the selection of alternative products.