If there is a hard lump or pimple under the armpit and there is purulent material after squeezing, it is considered to be an infection of the subcutaneous soft tissue, most commonly an infection secondary to a sebaceous cyst, which is a common benign disease, because there are more sebaceous glands in the armpit area and they are more widely distributed, and poor local hygiene can easily lead to sebaceous gland obstruction and poor emptying, forming a powder tumor, which can easily become secondary to infection. The typical symptoms are local pain, redness, swelling, congestion, and even fever. If an abscess is evident, surgery should be performed in a timely manner for incision and drainage, and after surgery, attention should be paid to regular drug changes and anti-infection treatment. During the treatment period, it is also necessary to prevent the occurrence of upper limb edema, and the affected limb should be elevated to promote venous blood return. During the treatment and recovery period, it is important not to eat spicy food and preferably not to drink alcohol, which can easily affect the wound healing and even lead to the occurrence of wound scar tissue hyperplasia.