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 ...

Cysts and boils, while similar, differ in cause and appearance. A boil is red or discolored, swollen, and contains pus, like a pimple. A cyst is under the skin and is usually painless but can resemble ...