A boil is an abscess. The word just tells you where it started.
An abscess is any walled-off pocket of pus. It can form anywhere in the body, from any source of bacteria.
A boil is an abscess that began in a hair follicle. Same pus, same wall, same treatment. That is why boils turn up where hair and friction meet — the back of the neck, the armpit, the thigh, the buttocks, the waistband line.
So the honest answer to "is it a boil or an abscess" is usually "both." What actually matters is size, how fast it is growing, and whether you feel unwell.
Bacteria — usually Staphylococcus aureus — get into the follicle and your body walls them off.
A follicle, a cut, an injection site, an ingrown hair, a ruptured cyst, or a spot with no obvious entry point.
An abscess can be small enough to drain itself or large enough to need a clinic.
Comes to a yellow or white head as it matures.
The centre softens as it fills — clinicians call that fluctuance. It feels like a small water balloon under the skin.
Multiple connected boils in one mass. Deeper, more likely to scar, and more likely to need clinical drainage.
Ten minutes, three or four times a day, encourages a small one to come to a head and drain on its own.
A clinician numbs it, opens it, and lets the pus out. Relief is usually immediate.


If "boils" keep coming back in the armpits, groin, buttocks, or under the breasts, they are often not boils at all. That pattern — the same few areas, repeatedly, sometimes with tunnels or rope-like scarring between them — is hidradenitis suppurativa.
It is a long-term inflammatory condition, not a series of infections. That is why each course of antibiotics helps a little and never settles it. It is commonly mistaken for bad luck with boils for years before anyone names it, and naming it is what unlocks treatment that actually works.
If you have had more than two or three in a skin fold, say that pattern out loud to a doctor rather than presenting each one as a fresh problem.
Different thing wearing the same word. A tender bump on the gum is usually a dental abscess draining from an infected tooth root. It will keep returning until the tooth is treated, so that one goes to a dentist.
Pressing on a walled-off pocket can push bacteria deeper into the tissue instead of out through the skin. On the face, especially around the nose and upper lip, that carries real risk and needs medical attention rather than a home attempt.