Hairless armpits may be caused by congenital heredity, young age and hormone deficiency. 1. Heredity: If the parents do not have hairy armpits or have less body hair, it may lead to a higher chance of hairless armpits in the next generation. 2. Young age: If you are young and your body is not fully developed, you may not have hairy armpits, which is a normal physiological phenomenon. 3. Hormone insufficiency: armpit hair usually grows under the stimulation of androgen, if the body androgen secretion is insufficient, it will lead to low androgen levels, and there may be a case of armpit hairlessness. In daily life, you need to pay attention to armpit hygiene, suggest a light diet, strengthen nutrition, and eat more food rich in vitamins and proteins. After eliminating congenital and physiological factors, if the underarms still do not grow hair, it is recommended to go to the hospital in time for consultation and treatment.