Seborrheic alopecia: It is a type of hair loss that occurs on the basis of excessive seborrhea, often accompanied by increased dandruff, often greasy scalp, painful and itchy. Seborrheic alopecia, also known as male pattern baldness and androgenic alopecia, is related to genetics, androgens and seborrhea. The symptoms are excessive oil production in the scalp and greasy feeling of the hair. The clinical manifestations are excessive scalp fat overflow, resulting in a greasy and moist scalp, combined with dust and dandruff mixed, a few days without washing the hair is very dirty, and emits a foul smell, especially when the temperature is high; sometimes accompanied by scratchy scalp inflammation, mainly due to the scalp humidity, bacterial growth infection caused by seborrheic dermatitis. Normal people on average lose about 70-100 hairs per day, which is a normal metabolism, and the number of hairs shed and new hairs per day is approximately the same, so it will not become thinner. If the number of hair loss exceeds this number, and the hair is significantly thinner than before is pathological hair loss, if usually not much hair loss, but the hair growth is very slow, hair thinning, this also belongs to pathological hair loss. The main reason for seborrheic alopecia is the accumulation of excessive sebum secretions around the hair follicles, even pressing or blocking the pores of the hair follicles, creating obstacles to the normal growth of hair, in addition, the excess of oleic acid and linoleic acid in sebum secretions has a toxic effect on the hair follicles, resulting in hair poisoning, withering and shedding. Seborrheic alopecia mostly occurs in young adults with strong sebaceous secretion, and hair loss gradually starts from the top of the head and spreads to the forehead. The scalp is greasy and bright red with yellow oily scabs.