The hair loss mentioned here refers to pathological hair loss. It can be examined by observing the number of hair loss, hair density and hairline, and if necessary, it can also be examined by dermoscopy directly in the hospital. 1. Normal people will not lose more than 100 hairs per day, if the number of hairs lost per day exceeds this indicator, it indicates the existence of pathological hair loss. 2. The density of hair in the unit area is found through observation. If the density decreases or the hairline moves up significantly, it indicates the existence of pathological alopecia. 3. Dermoscopic examination: through the dermoscopy can zoom in to observe the situation of hair follicles, such as hair follicles in the unit of the number of hair significantly reduced, hair thinning, soft, are suggestive of the existence of pathological alopecia. If hair loss is suspected, it is recommended to go to the hospital in time, complete the relevant examinations, make a clear diagnosis and treat the symptoms to avoid more serious consequences.