Cyst Growing Under the Skin: What You Should Know

An epidermoid cyst contains keratin inside a lining. Continued build-up can make the lump more noticeable, while irritation or inflammation can cause a faster change with soreness, redness, or warmth. A cyst may also look larger because surrounding tissue has swollen. Growth alone cannot confirm the diagnosis: other skin lumps can enlarge for different reasons.

Note when the change began, whether the skin is hot or discoloured, and whether fluid is draining. Those details help a clinician assess the difference between a quiet cyst, an inflamed cyst, and an abscess. Do not try to determine this by forcing the lump open.

Arrange a medical review for a lump that is steadily enlarging, repeatedly returning, or becoming uncomfortable. Until then, keep the skin clean, avoid friction, and use a clean warm compress if it is tender. Do not squeeze, lance, or massage it; these actions can worsen inflammation and make the edges harder to assess.

Depending on the findings, treatment may include a [Steroid Injection Into The Skin](/treatments/injectables/intralesional-steroid-injection/) for selected inflammation, [Abscess Drainage](/treatments/minor-procedures/abscess-drainage/) when a pus collection is present, or [Cyst Removal](/treatments/surgical-dermatology/cyst-removal/) for a recurrent or bothersome cyst. Your clinician will match the option to the current condition of the skin.

You can also read about [Skin Lumps](/symptoms/skin-lumps/) to compare common presentations.

Get prompt care if enlargement is accompanied by increasing pain, heat, spreading redness, pus-like drainage, or fever. Seek urgent help if swelling affects vision, causes severe facial pain, or makes breathing difficult. A lump that is hard, fixed, persistently bleeding, or changing without signs of ordinary inflammation should be assessed rather than watched indefinitely.

Ask whether the growth appears to reflect filling, inflammation, or infection, and whether the lesion should be observed or treated. Clarify what wound care is needed, whether a sample or further assessment is appropriate, and which warning signs should bring you back sooner.