A cyst is a sac or cavity that may be filled with pus, semi-solid material, or air. It doesn’t usually cause pain until it gets large. An abscess is a painful, red infection that’s filled with pus. A ...

A sebaceous cyst is a small pocket filled with a cheesy fluid that forms beneath the skin. They usually caused by swollen hair follicles. Most often they're harmless and disappear by themselves but if ...