What should you know about a cyst under the skin?

An epidermoid cyst can feel like a round, smooth lump beneath the skin and may have a small opening at its surface. It can stay quiet for a long time, then become swollen or sore when the surrounding tissue is inflamed. A new lump is not automatically a cyst, so a clinician may examine its texture, mobility and skin changes. Skin lumps can have several causes; learn more in the guide to Skin Lumps.

Keep the area clean and avoid pressing, puncturing or trying to empty it. Friction from clothing or repeated touching can irritate the surface. If it opens, cover it with a clean dressing and wash your hands after contact. A clinician may discuss observation, an intralesional steroid injection for inflammation, drainage when there is a collection, or cyst removal when the sac keeps returning or causes trouble.

Arrange prompt medical review for spreading redness, increasing warmth, worsening pain, pus-like drainage, fever, red streaks, or a lump that grows quickly. Seek urgent help if you feel very unwell or the swelling affects breathing, swallowing or vision. Even without these warning signs, a persistent or recurrent lump deserves an examination before treatment is chosen.

Ask whether the lump has features of an epidermoid cyst, whether inflammation or infection is present, and whether its sac remains beneath the skin. You can also ask which option fits its location, what wound care would involve, and what changes should trigger an earlier review.