The head of the head for no reason, may be common warts, epidermal cysts, boils and other diseases caused. 1. Warts are caused by human papillomavirus infection and can appear as round bumps the size of a pea. If warts occur on the head, they can cause bumps on the head for no apparent reason. 2. Epidermal cysts: the cause of the disease is mainly embryonic ectopic, skin trauma, pore blockage and other factors caused by the head. A dome-shaped elevated skin swelling will appear locally. 3. Boil: the cause is mostly caused by Staphylococcus aureus infection, which is most common in the head, face and neck. Patients will appear one or more red, hemispherical painful nodules. There are many reasons why a bag may appear on the head for no reason, so it is recommended that the patient go to the hospital and get a clear picture of the cause of the problem.