Hair loss is divided into physiological hair loss and pathological hair loss. The hair itself has a cycle of growth and decline, and hair loss is accompanied by hair growth every day, maintaining a stable state of dynamic balance in terms of quantity. In general, the number of hair loss within 100 per day is a normal physiological phenomenon, but if you lose more than 100 hairs per day for three consecutive months, hair gradually thinning or hair loss spots, then it is pathological hair loss, should pay attention to it and go to the regular hospital dermatology department as soon as possible. So what are the common causes of hair loss? 1, androgenic alopecia Androgenic alopecia is a kind of hair loss with genetic factors involved and dependent on the role of androgens, both men and women can be affected. The reason for hair loss is that the androgens in the body are relatively too high or the local hair follicles on the scalp are too sensitive to androgens, resulting in the miniaturization of the hair follicles and the gradual thinning and softening of the hair and its loss. 2.Nutritional deficiency alopecia, dieting, anemia, chronic wasting diseases, etc. can make the local nutrition supply of the scalp insufficient, so that the normal growth of hair is inhibited and enters the resting phase in advance, thus causing diffuse thinning of hair. 3, hair loss caused by mental factors Excessive anxiety and tension, mental stress, insomnia, etc. can lead to neurological disorders, the latter can make the local blood vessels of the scalp in a long time in a state of contraction, the blood supply of the hair follicle is insufficient and the abnormal loss of hair. 4, postpartum hair loss Postpartum hair loss refers to the large amount or abnormal loss of hair after the birth of women, which is related to the changes in the level of estrogen in the body before and after pregnancy. During pregnancy, the body estrogen increases, the life span of hair is extended, and some of the hair is “overdue for service”. After delivery, the estrogen level in the body decreases to normal, and the hair in the “over-servicing period” are “retired” and fall off. In addition, postpartum hair loss is also related to mental tension and lifestyle changes. Postpartum hair loss is only a kind of temporary hair loss, there is no need to be nervous after appearing, generally in about 6-12 months after giving birth will recover on its own. Age-related hair loss. Hair follicles, like people, are also alive, with the growth of age, hair follicles will gradually decline, atrophy, hair growth and metabolic function decreases, the number of new hairs gradually reduced, resting and regression of the hair gradually increased, resulting in hair loss gradually thinning. In addition, other causes of hair loss are baldness “ghost shaving”, lupus erythematosus, lichen planus, syphilis, etc. If abnormal hair loss occurs, it is recommended to go to the regular hospital dermatology department in a timely manner, under the guidance of professional doctors, to determine the cause and standardize treatment.