Sudden loss of hair in a circle may be due to seborrheic dermatitis, androgenetic alopecia, ringworm of the head, etc., which can be treated with reasonable medication. 1. Seborrheic dermatitis (1) Topical medication: apply metronidazole gel, compound miconazole cream, compound econazole suppository or use selenium disulfide lotion. (2) Oral medication: Itraconazole capsules can be used for 2 to 3 weeks, and vitamin B6 and vitamin B2 can be taken appropriately to improve the symptoms of sebum overproduction. 2. Androgenetic alopecia: men use 5% minoxidil tincture, women use 2% minoxidil tincture applied to the affected area. For severe cases, men can take Finasteride orally and women can take Spironolactone orally. 3. Tinea capitis: topical antifungal drugs, such as 1% terbinafine cream, bifonazole gel; oral terbinafine, itraconazole and other antifungal drugs. At the same time, we should pay attention to the patient’s personal hygiene, avoid sharing personal items with others to avoid cross-infection. Hair a circle of sudden loss may also be malnutrition and other factors, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor to standardize the use of medication, not blindly self-medication.