What should you know about a purple sebaceous cyst?

Skin over a cyst may look purple when it is inflamed, stretched, bruised, or affected by pressure. A darker area can also appear after the cyst has leaked or been rubbed. Colour alone cannot identify the cause of a lump, so note its texture, warmth, tenderness, and speed of change.

A cyst may have a visible central pore, but a clinician should check any lesion that looks unlike your previous cysts or does not settle. Avoid picking at a discoloured surface.

Take a clear photograph in consistent lighting and arrange a skin examination, particularly if the purple colour is new or spreading. Protect the area from pressure and friction, and cleanse it gently without scrubbing.

Depending on findings, care may include observation, an injection into the skin for inflammation, drainage of a collection, or removal of the cyst sac. Do not attempt any of these at home.

Seek prompt attention if purple skin is rapidly enlarging, hot, very painful, blistered, bleeding, or accompanied by pus or fever. Get urgent help for rapidly spreading swelling, faintness, breathing difficulty, or swelling near the eye.

Ask whether the colour suggests inflammation or bruising, whether the lesion needs drainage or removal, and what changes should prompt an earlier review.