Selenium dioxide lotion, whose correct name is selenium disulfide lotion, is useful for treating dandruff, seborrheic dermatitis of the scalp, lichen planus, and combating seborrhea. There are differences in usage due to the different diseases treated. Selenium disulfide lotion belongs to the skin antifungal drugs, its main ingredient is selenium dioxide, clinically used for the treatment of dandruff, seborrheic dermatitis of the scalp, lichen planus and the control of seborrhea role. When patients use it for the treatment of dandruff and seborrheic dermatitis of the scalp, they can wash their hair and scalp first, then take 5 to 10 grams of the solution and apply it to the hair and scalp, gently until it foams. Wait for 3 to 5 minutes, then rinse off with warm water and repeat if necessary. Frequency of use 2 times a week, a course of treatment 2 to 4 weeks, in severe cases can be repeated 1 to 2 courses of treatment. For the treatment of lichen planus, first clean the affected area, then according to the area of the affected area to take 10-30 grams of liquid medicine to apply evenly, wait 10-30 minutes and then wash off with warm water. The frequency of use is 2 times a week, a course of treatment for 2 to 4 weeks, and can be repeated for 1 to 2 courses of treatment in severe cases. Some patients may experience adverse reactions such as hair discoloration, contact dermatitis, alopecia and scalp dryness after use. Patients with skin lesions, skin inflammation and skin with oozing areas are prohibited from use. Note that this product should not be used within two days after hair coloring and perming. When patients need to use selenium disulfide lotion, it is recommended to use it under the guidance of a doctor and not to use it privately.