A hard bump behind the root of the ear is considered to be possibly caused by a disease. If symptoms such as redness, swelling and pressure pain occur, it may be a sign of swollen lymph nodes. In addition, it may also be caused by improper cleaning behind the root of the ear, causing local sebaceous cysts and folliculitis. Therefore, it can be identified by the following characteristic symptoms: 1. Swollen lymph nodes behind the ear: There are lymph nodes behind the ear distributed at the root of the ear. The main clinical manifestation of swollen lymph nodes is a hard nodule with large local volume, redness, swelling and pressure pain, resembling a hard lump. Some patients may have hearing loss, swollen parotid glands, sore throat and other inflammatory symptoms. It can be treated with oral azithromycin, ciprofloxacin and other antibiotics. 2. Ear root sebaceous cysts: usually caused by blockage of sebaceous ducts in the ear root area, usually appearing as round hard bumps of different sizes with smooth surface, clear borders and elasticity. The cysts have a black pinpoint-sized depression in the center, and the white paste-like, foul-smelling contents can be squeezed out. At present, the treatment of sebaceous cysts is mainly based on surgical treatment, and most patients can be cured by complete removal of the cysts; 3. Folliculitis of the ear roots: Folliculitis of the ear roots usually also results in the symptoms of hard bumps behind the ear roots, and most patients also have itching and pain, and patients can follow the instructions to promote the elimination of inflammation by using topical vitamin A cream, clindamycin ointment, and erythromycin ointment. In addition, localized hard bumps behind the ear without obvious pain, redness or swelling may also be subcutaneous fibroids in the skin behind the ear, but they are relatively rare. If it affects the patient’s daily life, it is recommended to go to the hospital to improve the relevant examination to clarify the diagnosis.