Cosmetic dermatitis, also known as cosmetic contact dermatitis, refers to irritant contact dermatitis and allergic contact dermatitis caused by contact with cosmetics. Irritant contact dermatitis: caused by cosmetics containing irritating ingredients, such as depilatories, deodorants, etc., often have more contacts. The patient has a history of exposure to such cosmetics and skin irritation occurs relatively soon after exposure. The lesions are confined to the contact area and are well-defined; they appear as acute or subacute dermatitis with papules, edema, blisters, vesicles, exudates and crusts after breaking. Local pruritus, burning or painful sensation is felt. The severity of the lesions and the time of onset are significantly related to the concentration of the exposure and the length of exposure; they can be cured after removing the cause. Allergic contact dermatitis: This type of cosmetics is not irritating, such as most of the cosmetics commonly used. The majority of exposed individuals do not develop the disease, but only a small number of allergic individuals. Patients have a history of using such cosmetics and have a certain incubation period; lesions tend to occur at the site of contact, but can also spread to the periphery in severe cases. The lesions are polymorphic in form, with erythema, papules, blisters, skin swelling, etc., and itching. The lesions often persist. A positive patch test is an important basis and reliable method for diagnosing cosmetic dermatitis, and a positive test can be diagnosed as cosmetic contact dermatitis; however, a negative test cannot exclude the diagnosis, but should be combined with the medical history and clinical manifestations for a comprehensive analysis. In addition, false-positive and false-negative results should be excluded. The patch test should be done after the dermatitis has been controlled and stabilized or cured for some time. The irritating cosmetics (such as depilatories, deodorants, etc.) should not be used for the patch test. After the diagnosis of cosmetic dermatitis is confirmed, all suspected cosmetics should be discontinued immediately, and the residual cosmetics on the skin should be removed in a timely manner. And give anti-allergic therapy and symptomatic treatment. After the above treatment, generally 1-2 weeks can be cured. If the cause is not removed in time and other types of cosmetics are used at the same time, some highly sensitive people may have cross-allergies or multiple allergies, and the dermatitis is prone to recurrence, or to become chronic and persistent. Therefore, when cosmetic contact dermatitis is suspected, you should stop using all cosmetics and go to the hospital dermatology department as soon as possible to confirm the diagnosis and treatment.