A hard bag on the foot that is painful to press is considered to be a boil. A boil is an acute purulent inflammation of the deeper parts of the hair follicle and the surrounding tissues, often induced by Staphylococcus aureus infections. The rash is initially a follicular inflammatory papule with obvious basal infiltration, and then the inflammation expands to form a hard nodule around it, accompanied by redness, swelling, heat, and pain. Topical medication is the mainstay of treatment, and early and non-suppurative patients can be treated externally with 20% ichthyolipids ointment, mupirocin ointment, and fusidic acid ointment, and macrolides, cephalosporin, and quinolone antibiotics are also available. Also considered sebaceous cysts, itself no self-conscious symptoms, easy to secondary infection, resulting in local redness, swelling, heat, pain of the inflammatory reaction, you can use topical antibiotic ointment, such as compound polymyxin B cream, erythromycin ointment, etc., can be surgically excised after the inflammation subsides.