2023 Volume 47 Issue 1 Pages 22-27
Allergic contact dermatitis from products used on the scalp causes symptoms not only on the scalp, but also on the face, neck, and back. Some products, such as oxidative hair dye, produce a generalized contact dermatitis syndrome. It is difficult for dermatologists to recognize that dermatitis on the face is allergic contact dermatitis caused by products used on the head. The continued treatment with topical tacrolimus ointment or topical steroids, without excluding the causes of the exacerbation, may lead to the development of additional skin diseases such as rosacea-like dermatitis. There are also cases of delayed allergic contact dermatitis caused by oxidative hair dye, which may lead to anaphylactic symptoms after repeated exposure. It is extremely important to diagnose allergic contact dermatitis before it becomes severe and to eliminate allergens from the patient’s life.
Patch testing is most useful in finding the cause. Even if the patch test is positive for a product, if the causative allergen cannot be determined, there remains the possibility that symptoms will not improve even if the patient changes the products they use. In addition, patch testing with the product may give false-negative results, so it is advisable to patch test the allergen at the same time along with the product. Japanese baseline series and cosmetics-related allergens are applied, but it is difficult to obtain cosmetics-related patch test allergens in Japan. Even commercially available allergens may give false-negative results depending on the reagent. It would be more diagnostic if raw materials could be provided by the manufacturer of the product that tested positive in the patch test.
In this paper, we will provide specific examples of cases of contact dermatitis caused by products used on the scalp and describe the problems involved in diagnosing allergic contact dermatitis and determining its cause.
