Hair loss in a 15-year-old girl every day may be physiological alopecia or pathologic alopecia, such as ringworm of the head, seborrheic alopecia, and other causes (e.g., malnutrition). 1. Physiological alopecia: there are three periods of hair growth, i.e. anagen, telogen effluvium and anagen, and some of the hairs in the anagen phase may fall out naturally, but generally the number of hairs falling out is limited, and the amount of hairs falling out per day is usually less than 100. 2. Pathological hair loss: (1) Tinea capitis: it is mainly caused by the infection of the scalp and hair by dermatophytes, which is infectious, and the inflammation can directly destroy the hair follicles or form scars, thus causing hair loss. (2) Seborrheic alopecia: also known as androgenetic alopecia, androgen in female patients in the pathogenesis is not yet clear, may be related to the decline in the concentration of sex hormone-binding proteins, free testosterone elevated, and so on, so as to appear follicle atrophy and the formation of hair loss. (3) Other causes: common such as malnutrition, etc., hair growth requires protein, trace elements, etc., if the lack of protein, vitamins, trace elements, etc., due to picky eating, absorption disorders, etc., the generation of hair may be affected, resulting in massive hair loss. If a 15-year-old girl loses more than 100 hairs per day, it is recommended to go to the dermatology department of a regular hospital for a clear diagnosis and standardized treatment under the guidance of a doctor.