Girls 18 years old legs hairy, may be related to heredity, the body’s hormone secretion level and bad habits and other factors. 1. Genetic factors: hair growth rate, density and color changes are related to genetic factors, the family has more body hair in the population, again the number of body hair will increase significantly. 2. Hormone secretion level: the growth of hair is affected by the level of androgen secretion in the body, women in puberty androgen secretion is more vigorous, the number of body hair will also appear to be more. 3. Bad habits: Repeatedly shaving body hair or using depilatory cream to remove body hair can lead to subsequent growth of body hair to become dense. Girls 18 years old legs hairy may also be caused by other reasons, it is recommended that the patient timely to the hospital, improve the relevant examination to clarify the cause of the disease, follow the doctor’s instructions standardized treatment.