Some girls do not have pubic hair down there, most of them are caused by genetic factors, a few are caused by pathological factors. 1. Most girls begin to grow pubic hair under the action of hormones in their bodies after they enter puberty. However, a few girls are affected by genetic factors, the hair follicles in the vulva are not sensitive to hormones, and even when they reach adulthood, they do not grow pubic hair, which is generally a normal physiological phenomenon, and there is no need to worry. 2. In a few cases, if a girl suffers from hypothyroidism, low ovarian function and other diseases, it can also cause scanty pubic hair or even no pubic hair at all, which belongs to pathological phenomenon. Girls who do not grow pubic hair due to pathological factors are often accompanied by slow growth, irregular menstruation, low libido, amenorrhea and other symptoms, and should seek medical attention in a timely manner.