In general, the hair can grow 4.5-6.0mm in half a month, and the normal human hair can grow 0.3-0.4mm per day on average. 2, genetic factors: usually genetic factors determine the growth of hair, different skin color, hair growth are different; 3, drug factors: if taking some immunosuppressive drugs, may make the hair growth slow or stop growing; 4, endocrine factors: if long-term mental stress, physical overwork and long-term stay up late, etc., may If the adrenal cortex, thyroid gland, anterior pituitary gland and other functional disorders, affecting the growth of hair; 5, disease factors: suffering from seborrheic dermatitis, ringworm, folliculitis and scalp trauma, etc., may cause part of the hair follicle function atrophy, hair loss, or no longer grow; 6, other: in general, women’s hair growth rate will be faster than men, healthy young people’s hair Growth is also faster than the elderly and children. In addition, the seasonal climate will also affect the hair growth, for example, the growth rate is faster in summer, while in winter there will be a slowdown. Therefore, it is recommended that you keep your scalp clean and hygienic, and eat more foods that are good for hair growth, such as black sesame and black beans. You should take outdoor exercise and avoid staying up late for a long time to ensure that your body gets enough rest to promote the growth of hair.