Five-year-old children with hard lumps under the skin of the jaw may be considered to be related to inflammation of hair follicles, submandibular lymphadenitis, sebaceous cysts and other factors. 1. Inflammation of hair follicles: in addition to the manifestation of hard lumps, it will be accompanied by local redness, swelling, heat, pain and other inflammatory symptoms. At this time, you can locally apply mupirocin ointment and so on to eliminate inflammation. To a certain extent, relieve the symptoms. 2. submandibular lymphadenitis: oral or respiratory tract infection, or submandibular gland inflammation, will cause localized lymph node swelling, manifested as hard lumps, sometimes accompanied by pain, fever and other symptoms. At this time, under the guidance of the doctor, oral amoxicillin and metronidazole tablets, etc., can effectively alleviate the lymph node swelling caused by inflammation. 3. Sebaceous cysts: When the opening of sebaceous glands is blocked, lumps are easily formed. With the secretion of sebaceous glands, the lumps will gradually increase in size and are benign. There may be other reasons for the above situation, it is recommended to go to the hospital. It is recommended to go to the hospital to identify the cause of the problem and treat the symptoms. Medications should be prescribed by the doctor.