The main cause of the formation of the sacrococcygeal hair-hiding sinus is not clear, and it is currently believed that the cause of the disease can be divided into congenital factors and acquired. Congenital skin depression and other conditions can cause the occurrence of this disease; acquired buttocks are often stimulated, the tip of the hair pierces the skin in the vicinity, forming a short pipe, while the hair is still connected to its root, the short pipe is then dermalized, when the hair is shed by the original hair follicle, it is inhaled by the gravitational force generated by dermalized short pipe and formed. I. Main etiology 1. Congenital factors: the hidden hair sinus in sacrococcygeal area may be due to congenital residual epithelial tissue, or congenital skin depression. It may also be the result of a deformed development of the central suture in the sacrococcygeal area, leading to the formation of cysts, which causes the disease.2. Acquired factors: The disease may also be formed later in life rather than a congenital disease, and the tendency of recurrence of the hidden hair disease after extensive surgical excision supports this theory. Occasional hair hiding cysts in places other than the buttock sulcus (such as the umbilicus, scalp, interfinger space, and between the breasts) also support the theory of acquired formation. Hidden hair sinuses also occur in areas where hair may cause localized damage, such as on the hands of barbers, shearers, and dog groomers. Second, predisposing factors overweight, obesity, local trauma or irritation, habitual sedentary lifestyle, and people with deep hip grooves are susceptible to the disease.