Hair loss can occur when washing or combing your hair, which is considered to be related to a variety of factors. If you lose less than 100 hairs per day, this is physiological hair loss. The hair growth cycle includes anagen, regression and resting phases. The hair that is shed when you comb your hair or wash your hair is mostly hair in the resting phase, and new hair will grow back in the follicle after it is shed. Also consider the case of pathological hair loss, such as androgenetic alopecia, which is a limited or disseminated hair loss caused by genetic factors. The causes are related to hormone levels and follicular androgen receptor polymorphisms, such as baldness, which is mainly caused by disorders of the autoimmune mechanism. Neuropsychiatric alopecia is mainly due to excessive mental stress, disturbance of phytoconstriction or central nervous function, strong and persistent local microvascular constriction of hair follicle papillae, resulting in local blood circulation disorder and hair loss.