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 cyst is a sac of fluid that forms a lump beneath the skin. Sebaceous cysts are hard lumps filled with keratin, the thick greasy protein which hairs are made from and which lubricates the top layer ...