Lichen planus, or lichen planus chaffer, is a superficial infection caused by Malassezia violating the stratum corneum of the skin, and the medications that can be used externally to treat it are ketoconazole lotion, selenium disulfide lotion, and terbinafine hydrochloride ointment. Ketoconazole lotion is an antifungal drug used to treat and control flaking, scaling and itching, it can relieve the skin symptoms of florid chafing rash, and it is contraindicated for those who are allergic to ketoconazole or other ingredients of this drug. Selenium disulfide lotion is an antifungal drug for skin use, it can be used to remove dandruff, treat seborrhea, seborrheic dermatitis of the scalp and florid chafing rash. It is contraindicated in areas of inflammation and erosion of the skin. Terbinafine hydrochloride is an antifungal drug, commonly used in the treatment of ringworm, tinea pedis, tinea corporis, tinea pedis, and cutaneous candidiasis, and can also be used for vulvovaginal candidiasis. Serious liver and kidney insufficiency should not be used. In addition to medication, patients should pay attention to the skin hygiene and care of the lesions on weekdays, do a good job of cleaning, eat less spicy food, and maintain a regular routine. If the diagnosis of florid furuncle, it is recommended that patients seek medical advice in a timely manner, under the guidance of the doctor’s treatment, and not unauthorized use of medication, in order to avoid delaying the condition.