Dandruff is generally caused by Malassezia infection in fungi, and the drug shampoo for dandruff is the shampoo containing antifungal ingredients, and there are three common drug shampoos for dandruff as follows: 1. Ketoconazole lotion: low concentration of ketoconazole can inhibit the synthesis of fungal ergosterol and play the role of inhibiting the reproduction of Malassezia, and at high concentration it directly destroys the fungal cell membrane, showing an extremely strong fungicidal effect. Ketoconazole has a high affinity for scalp proteins and can quickly form a protective film on the surface of the scalp, thus sustaining its action. In addition, ketoconazole has a high safety level and will not be absorbed through the epidermis into the systemic circulation; 2. Selenium disulfide lotion: the main component is selenium disulfide, which has anti-seborrhea and antifungal effects. It acts on the surface of the scalp, can quickly play a therapeutic role, and the use of mild non-stimulating, also has a relatively good effect on lichen planus; 3, coal tar lotion: the main active ingredient is pure coal tar, can inhibit the secretion of abnormal sebum, has a bactericidal, anti-itch, anti-inflammatory effect, can also repair damaged hair. Anti-dandruff medicated shampoo should not be used when there is a break in the scalp, and do not contact the eyes and other mucous membranes, such as the mouth and nose. If there is burning sensation, redness and swelling in the area where anti-dandruff medicated shampoo is used, stop using it immediately, wash the shampoo, and consult a physician if necessary.