What is a boil?
A boil is a pus-producing inflammation of a hair follicle. Superficial inflammations of hair follicles are called folliculitis; the deeper inflammations are called boils. When one pus head is visible we speak of a furuncle; when several pus heads are visible in one inflammation we call it a carbuncle.
How do boils develop?
Almost always the bacterium Staphylococcus aureus can be demonstrated in the pus of a boil. This very common bacterium can also cause erysipelas, and not rarely the boil is the source from which an erysipelas infection develops. The bacterium can be transmitted, among other ways, by the fingers. When, through a break in the skin, the bacterium is “planted” near a hair follicle, it can grow out and cause an inflammation, which leads to tissue death and pus formation; eventually the pus discharges through the skin.
Who gets them?
Some people are “carriers” of S. aureus, meaning they carry the bacterium without any trouble. It is estimated that about 10% of the population are carriers. Known hiding places are the nasal cavity, the ear canal and the area around the anus. Carriers do not necessarily develop boils, but they have a greater chance because they are much more exposed to the bacterium. Most people who regularly develop boils are otherwise completely healthy, though some patients have immune disorders, diabetes or anaemia.
How are boils treated?
In most cases the boil discharges on its own after “ripening”. This ripening can be speeded up by applying warm, moist compresses. Do not try to squeeze the boil, as this will only worsen the inflammation. In case of doubt consult your doctor, who can drain the boil surgically if needed. When there are several boils, and especially when further spread of the bacterium seems to be starting, your doctor may consider prescribing an antibiotic, and will take pus to identify the bacterium (and any antibiotic-resistance pattern). If carriage of S. aureus is established (by culturing the ears/nose/buttocks), a topical antibiotic is also applied to those sites.
How can I prevent boils?
With existing boils, or if you are at increased risk, try to be as hygienic as possible: wash the skin daily with a mild disinfectant soap, wear clean underwear, do not pick at your nose and ears, and try to avoid friction of the skin (and thus microscopic skin damage). Do not use towels shared with household members, as this can transmit the bacteria to others. Consult your doctor for regularly recurring boils.
When to see a doctor
See a doctor if a boil is large, very painful, on the face, accompanied by fever or spreading redness, if you have several, or if they keep coming back.