An abscess is a pocket or ball of pus inside the body. Pus is a combination of bacteria (a type of germ) and white blood cells (part of our immune system’s defenses that fight germs). An abscess can occur under the skin, in which case it’s red, hot, and tender. It can also occur in the root of a tooth.
The most dangerous abscesses occur deep inside the body, like in the brain, lung, or abdomen. In those cases, symptoms are mainly fevers and drenching sweats. Lung abscesses cause a cough, brain abscesses a headache & maybe confusion. Low-grade, smoldering bacterial infections may simply cause fatigue and weight loss. Diagnosis is made by x-ray, CT scans, or other imaging.
The skin abscess can simply remain indefinitely. It can burst open (which often cures itself as the pus drains out), or the bacteria can spread to the bloodstream and even prove fatal. Treatment involves opening the abscess so the pus can drain; on the skin, it’s called an “incision & drainage” (I&D).
Antibiotics don’t cure an abscess, because the abscess has no blood supply. So the medication can’t get inside. Antibiotics can help stop the abscess from growing, and are part of treatment for internal abscesses (they’re given IV in a hospital). But surgery of some sort, including tooth extraction, is usually necessary.