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.

After melanosis faciei femina, two outbreaks of severe side effects caused by cosmetics have occurred since 2009. One is an immediate wheat allergy percutaneously sensitized to hydrolyzed wheat protein contained in facial soaps (HWP-IWA) that included 0.3% of a specific type of HWP, Glupearl 19S. A total of 2,111 cases developed allergic contact urticaria, anaphylaxis, and/or wheat-dependent exercise-induced anaphylaxis (WDEIA) after using the soaps.

The other one is Rhododenol-induced leukoderma (RDL) due to a skin-whitening agent rhododendrol (Rhododenol) (RD) approved by the Ministry of Health, Labour and Welfare as a quasi-drug. A total of 19,609 individuals developed leukoderma, that is about 2.4% of those who used whitening cosmetics (cosmetics) containing 2% RD.

The author served as chairpersons of the special committee of the Japanese Society of Allergology for HWP-IWA, and of the Japanese Dermatological Association for RDL. Both committees carried out epidemiological studies, established diagnostic criteria and provided practical guidance to treat and care the patients. Both committees performed and reviewed clinical, basic, and genetic research on the pathomechanism, and provided information to the medical doctors and the patients.

In this article, HWP-IWA and RDL are reviewed from a viewpoint of a dermatologist and the chairpersons of the special committees.

Adverse effects to cosmetics are multifactorial; of these, contact dermatitis is the most common, and shows eczematous reactions such as papules, erythema, and vesicles at contact sites with the causative agent. Contact dermatitis is classified into three types: irritant contact dermatitis, allergic contact dermatitis, and photocontact dermatitis. All are initiated by the penetration of a chemical. Its epicutaneous stimulus make keratinocytes secrete cytokines, and inflammation depending on the innate immune system. Allergic contact dermatitis is a delayed-type hypersensitivity reaction mainly involving T cells and antigen-presenting dendric cells. Recent studies demonstrated that the innate immune system plays an important role for its sensitization and expression of eczema phases. Photocontact dermatitis is produced from the combination of a skin contact with a compound together with ultraviolet light. Contact urticaria patients develop localized wheal immediately after direct contact with a causative substance. It is divided into three types: immunological, non-immunological, and one with unclear mechanism. Immunological contact urticaria is a type I sensitivity immunological reaction, and this type can produce anaphylactoid reactions. The mechanism of leukoderma due to rhododendrol is thought caused by the metabolite that is a product of rhododenol bound to tyrosinase. The metabolite produces reactive oxygen species and depletes the intracellular antioxidant glutathione, which to be responsible for melanocytes death. Cosmetics occasionally lead to exacerbation of skin diseases: e.g., atopic dermatitis and acne vulgaris. In such cases, most are produced by inadequate choice of cosmetics, respectively.

Cosmetics can cause allergic contact dermatitis, irritant contact dermatitis, contact urticaria, depigmentation, and other skin disorders. The skin testing methods for allergic contact dermatitis and allergic contact urticaria are described in this paper. A 48-h closed patch test, open test, or repeated open application test (ROAT) is used to diagnose allergic contact dermatitis, which is a delayed allergy. A photopatch test is required to test photoallergic contact dermatitis. Rinse-off cosmetic products should be diluted with 1% aqueous solution and applied for 48-h closed patch test, while powder products should be mixed with approximately 30% petrolatum and applied. Hair coloring agents and permanent wave agents with irritant properties should not be subjected to closed patch test but instead undergo an open test. It is also useful to perform a ROAT to diagnose allergic contact dermatitis. On the other hand, a prick test should be performed to diagnose contact urticaria, which is an immediate allergy.

There are various types of side effects caused by cosmetics; mostly they are believed to be not serious. Further, there are not a few cases at present that it is difficult to identify which ingredients in cosmetic products caused; even it was certainly caused by cosmetics which had been used. Table 1 shows not only the actual cases which were implemented some measures by MHLW (Ministry of Health, Labour and Welfare of Japan) under the jurisdiction of Pharmaceutical Affairs Law or JCIA (Japan Cosmetic Industry Association) as a representative of cosmetic industries, taking into account the cases must be caused by cosmetics (including quasi-drugs such as medicated cosmetics), but also covers the background and history of cosmetics regulation under the Pharmaceutical Affairs Law in considering the safety of cosmetics.

In this article, simple consideration is done on Melanosis Faciei Feminea which has developed social problem that health damage is caused by cosmetics. The process in pigeonholing a part of this case is investigated from an ethologic perspective. Furthermore, a lawsuit on melanosis and simple description on Berlocq Dermatitis are mentioned.