Boys have a lot of leg hair due to physiological factors, genetic factors, disease factors, drug factors, etc.; physiological factors and genetic factors lead to a lot of leg hair in boys, there is no effect on physical health, generally do not need treatment. 1. Physiological factors: male androgen secretion after puberty, can cause hair growth, resulting in increased leg hair. 2. Hereditary factors: men in the family who generally have a lot of leg hair are more likely to have hairy legs in their offspring. 3. Drugs: The long-term use of glucocorticoid drugs can also lead to a lot of leg hair, including other parts of the body will also appear hairy. 4. Disease factors: adrenal gland diseases such as primary aldosteronism can also lead to a lot of leg hair in boys. If you suspect that a disease is the cause of a lot of hairy legs in boys, you need to go to the hospital in time to see a doctor for treatment.