There are many reasons why hair grows fast, mainly related to external factors, personal factors, and genetic factors. 1. External factors: pay attention to hair care, timely cleaning of hair, remove the blockage in the root of the hair follicle oil, dander, is conducive to hair growth. Frequent massage scalp, combing hair, physical stimulation will accelerate the skin local blood circulation, promote hair growth. 2. Personal factors: dietary structure is scientific, reasonable, intake of adequate hair growth needs of protein, trace elements, vitamins, etc., hair nutrition is good, natural growth fast. If the exercise and regular work and rest, maintain a good state of mind, can also promote the whole body and skin blood circulation, help the scalp follicles to draw nutrients, hair will also grow faster. 3. Hereditary factors: how much hair, growth speed, often with the family genetics. If your parents, elders and other relatives in your family have faster hair growth, it will also be directly inherited to your children. Hair grows fast, you can cut your hair diligently, usually eat more food rich in protein and vitamins, dietary attention to meat and vegetables, but also can participate in outdoor sports, try not to stay up all night, to ensure that the sleep time and sleep quality.