The pursuit of beauty is a legitimate need of human life, and although the level of beauty required varies from one to another, and even varies widely, anyone has a requirement for beauty. The purpose of using cosmetics is mainly the desire to maintain, restore and cause beauty. Protective agents for skin and hair keep the human skin and hair healthy, thus expressing their natural beauty. Wrinkle reducers, blemish removers and hair dyes for the skin restore beauty that has been lost due to age or disease. However, while cosmetics meet people’s beauty needs, they also cause some troubles for users. The long-term casual use of a variety of cosmetics can cause various adverse reactions to the skin, the most common of which is cosmetic dermatitis. Although it appears only in a small number of people, its harm cannot be ignored because cosmetics are so widely used. The inflammatory skin reaction caused by the application of cosmetics is called cosmetic dermatitis. Among the various cosmetic ingredients, hair dyes and eyebrow dyes are the most allergenic, and various creams and oils are also a common cause of cosmetic dermatitis, with fragrances and fungicides being the main allergens. Cosmetic dermatitis is actually a contact dermatitis caused by makeup. The main characteristic of cosmetic dermatitis is that it occurs after several days or years of cosmetic use, and most patients often do not suspect that it is caused by cosmetics at the time of onset. The initial stage of dermatitis tends to be erythema with swelling and burning sensation at the site of cosmetic application, followed by the appearance of small papules and blisters. During the inflammatory process, there can be itching, pain, swelling and heat, and these symptoms can disappear or diminish quickly after the allergen is removed. The lesions can expand and worsen if not diagnosed and treated in time or if the causative agent in question is not removed. If these cosmetic products continue to be used, chronic dermatitis may develop. Therefore, if symptoms such as skin erythema and flaking appear on areas frequently exposed to cosmetics, such as the face, head, and hands, you should go to a regular dermatology clinic for timely consultation and treatment to alleviate the pain. In addition to medical history and skin examination, patch test is the key to diagnose cosmetic dermatitis. The patch test is used to determine the sensitivity of a person’s skin to the substance it is exposed to, and this treatment can be used to determine which substance is the allergen for cosmetic dermatitis. Patients can also bring their own suspect cosmetics for patch testing to determine which cosmetics can continue to be used. When cosmetic dermatitis is diagnosed, the first treatment is symptomatic, such as erythema, papules, edema can be cold wet compresses of 3% boric acid 2-3 times a day for 30 minutes each time; erythema, flaking can be topical creams or ointments containing corticosteroids. If the patch test shows an allergy to a certain fragrance or cosmetic, you should not use cosmetics containing such fragrance in the future, or change to other brands. However, various hair dyes, lip balms, nail lacquers, etc. mostly use the same ingredients, so switching to a different brand of product may not always be effective. The prevention of cosmetic dermatitis is extremely important, so do not change easily when using a cosmetic product that is well tolerated.