Why does a skin cyst cause skin lumps?

An epidermoid cyst develops when surface skin cells become enclosed below the skin instead of shedding normally. These cells continue making keratin, a thick protein material, which collects inside the sac. This produces a firm or rubbery, usually rounded lump. Some cysts have a small central opening, while others sit completely under the surface. A cyst can stay quiet for a long time, then become tender, red, warm, or larger if it becomes inflamed or ruptures.

Avoid squeezing, piercing, or repeatedly pressing the lump, since this can irritate the sac and introduce infection. Keep the area clean and note changes in size, tenderness, drainage, or skin colour. A clinician can examine the lump and discuss observation, treatment for inflammation, drainage, or removal of the cyst wall when appropriate. Drainage alone may not prevent the sac from filling again.

Book medical assessment if a lump is new, changing, painful, repeatedly inflamed, or leaking material. Seek urgent care for rapidly increasing swelling, spreading redness, fever, severe pain, or a lump near the eye or another sensitive area. A sudden change should be assessed rather than assumed to be a simple cyst.

Ask whether the lump has features of an epidermoid cyst, whether it should be monitored or treated, and what signs would mean you should return. Tell the clinician about previous episodes, drainage, trauma to the area, and any medicines that affect healing.