Hidden hair sinus, also known as hidden hair sinus tract or hidden hair cyst, this disease can be congenital or acquired, the age of occurrence is mostly in the age of 20-30 years after puberty, but some people report that it is more common in males around 49 years old, it is a chronic sinus tract or cyst within the soft tissues, and it is characterized by hidden hairs. Hair-hiding sinuses occur in the sacrococcygeal region, but can also occur in the scalp, ears, chest, umbilicus, and between the fingers and toes. Because the hair grows into the skin or subcutaneous tissue, making the cyst susceptible to infection, the sinus tract does not heal easily, and so clinically it presents as a chronic, painful, fluid-flowing sinus tract, which may have a localized inflammatory reaction, and occasionally squamous carcinoma can occur in those with chronic sacrococcygeal damage.