There is a painful lump at the root of the thigh, and the causes are considered as follows: 1. Boils: mainly due to chronic inflammatory skin disease of the hair follicle sebaceous glands at the root of the thigh caused by bacteria and fungi, which appear as red, raised nodules with a hard texture at the root of the thigh, which may become soft in texture after a few days, and a white head at the top, where bacteria can be detected by bacterial culture. In terms of treatment, in the early stages, if there is no suppuration, mupirocin ointment can be applied topically. If the pus is present in the late stage, an incision and drainage is needed in the dermatology department. Comfrey oil and epidermal growth factor gel can also be given for external use, and oral compound glycyrrhizin tablets and minocycline hydrochloride tablets are also needed. 2. keloid: mainly due to trauma, wounds or inflammatory skin diseases, the keloid appears after artificial squeezing with hands to form subcutaneous connective tissue hyperplasia. If this happens after rubbing by underwear or squeezing by hand, there is a possibility of pain. Fractional laser treatment is available in the dermatology department. Avoid spicy and irritating foods, alcohol, and squeezing the keloid with your hands. If the keloid becomes increasingly painful, oral anti-inflammatory medications such as roxithromycin capsules and topical medications such as mometasone furoate cream and fusidic acid cream can be applied topically. If necessary, local closed treatment, such as treatment with compound betamethasone injection or treatment with liquid nitrogen freezing, can also be performed in the dermatology department. Therefore, for patients with bumps on the root of the thigh with pain, it is recommended to go to a professional dermatologist at a regular hospital for appropriate consultation and treatment.