I. Definition of cosmetic dermatitis Cosmetic dermatitis (cosmetic dermatitis) refers to dermatitis caused by the use of cosmetics. Cosmetics on the market today are basically divided into two categories, simple and efficacious. The simple type is less problematic because it only covers, protects and moisturizes the skin, and the products are strictly controlled by the national authorities from development, production and quality testing. The most clinically “complex” type of cosmetics is the efficacy type. These products often have the promised effects of blemish removal, whitening, anti-wrinkle and acne removal, and are a class of special-purpose cosmetics, which should strictly speaking be drugs. Therefore, we call them pharmaceutical cosmetics. These products should be used under the guidance of a dermatologist. Products with blemish, whitening, anti-wrinkle and acne effects generally contain drug ingredients such as hydroquinone, retinoic acid, mercury and lead (some unscrupulous businessmen and enterprises illegally add prohibited ingredients, such as adding high concentrations of mercury to blemish removal products, which is impossible for reputable enterprises to happen. It is also not excluded that individual manufacturers add corticosteroids to counteract the stimulating effect of topical drugs). The short-term application of these products is effective, and can play a role in removing spots and flattening acne. However, long-term use or improper use can lead to side effects, such as skin depigmentation, photosensitivity, rebound from discontinuation and fetal malformation. China’s cosmetic regulations prohibit the presence of such substances in cosmetics or have strict limits on their concentration, and consumers are advised to consult a dermatologist beforehand when using whitening products. However, given commercial privacy, national policy and technical reasons, dermatology clinics do not have the ability or authority to identify the merits of products and test their ingredients. Only advice can be given to consumers on the use of cosmetic products. Or, to put it this way, one of the most likely results of long-term application of drug-based cosmetics is that the skin’s inherent physiology is altered, making the skin particularly sensitive. During the period of skin “hypersensitivity”, the skin may feel uncomfortable or irritated even if the most simple “protective” products are applied. Diagnostic points 1. The patient has a history of topical cosmetics. 2. The lesions are mainly on the area where cosmetics are applied, such as the face, neck, eyelids or mouth and lips. The lesions are flushed and edematous, with small blisters, blisters or vesicles on them. 4.Chronic cosmetic dermatitis is characterized by mild flushing, dry skin, a small amount of flaking, brick-colored pigmentation, and self-conscious itching discomfort. 5, take the allergic cosmetics for patch test is positive results. Treatment points 1, should immediately stop using allergy-causing cosmetics. 2, acute cases with 3% boric acid solution wet compress. For chronic cases, apply weak corticosteroid preparations topically. 3, oral antihistamines. 4. Cosmetics should be used again after an allergy test on the inside of the forearm, and only after 48-72 hours of negative results.