An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed.
Most abscesses are caused by an infection with staphylococcal bacteria. When bacteria enter the body, the immune system sends white blood cells to fight the infection. A cavity is created, which fills with pus to form an abscess. The pus contains a mixture of dead tissue, white blood cells and bacteria.