A large, swollen red lump with a yellow or greenish center can be a sign of a skin abscess, boil, or infected cyst. These conditions can look similar, but they have different causes. A skin abscess develops when pus collects beneath the skin, often due to a bacterial infection. A boil is a type of abscess that begins in an infected hair follicle, while an epidermoid cyst is a small sac beneath the skin that can become inflamed or infected.

Common symptoms include tenderness, warmth, swelling, redness, and a buildup of pus. Some lumps grow gradually, while others become painful and swollen over a short period. Although many are treatable, a large or worsening lump should not be ignored, particularly if the surrounding redness begins to spread.

How are these lumps treated? Small boils may improve with a clean, warm compress applied for 10–15 minutes several times daily. Larger abscesses may require incision and drainage by a healthcare professional, sometimes with local anesthesia. Antibiotics may also be needed depending on the severity of the infection. An inflamed cyst may require different treatment, and draining it alone may not prevent it from returning.

The most important precaution is never squeeze, puncture, or cut open a lump yourself. Seek urgent medical advice if it is very painful, hot, rapidly growing, or surrounded by spreading redness, or if you develop fever or chills. People with diabetes or weakened immune systems should be especially cautious. A medical examination is the safest way to identify the cause and determine the appropriate treatment.