What should you know about a flat cyst under the skin?

An epidermoid cyst is a sac beneath the skin that can contain keratin, a thick skin protein. It may look flat when it sits deep or spreads sideways, and the surface may have a small central opening. It can remain quiet, become tender, or swell if the surrounding tissue becomes inflamed. A cyst is different from an abscess, which is an infected collection that is often painful, warm, and increasingly red.

Because several types of skin lumps can feel alike, touch alone cannot confirm the cause. Note its location, firmness, mobility, colour, and whether it has changed.

Do not squeeze, pierce, or repeatedly massage the area; this can irritate the cyst and introduce infection. Keep the skin clean and avoid friction from tight clothing or shaving over it. Arrange a dermatology assessment if it persists, interferes with movement, or keeps returning. Depending on the findings, care may include observation, a steroid injection for inflammation, drainage when infection is present, or cyst removal to address the cyst wall.

Seek prompt medical care if the lump becomes rapidly larger, hot, very painful, red, or starts draining foul-smelling material. Fever, red streaking, or feeling unusually unwell also warrants urgent assessment. A lump that bleeds, breaks down, or changes in colour should be examined even without pain.

Ask whether the lump has features of a cyst, whether inflammation or infection is present, and whether it needs monitoring or treatment. You can also ask what signs should trigger a review and whether removal would leave a scar.