Boils

A boil (furuncle) is a red, painful, pus-filled lump in the skin caused by bacterial infection of a hair follicle. Boils can develop anywhere on the body, but are common on the face, neck, armpits, buttocks, and thighs — places with hair and friction. Most are caused by Staphylococcus aureus bacteria.

A carbuncle is a cluster of connected boils, usually on the back of the neck, shoulders, thighs, or buttocks. Carbuncles are larger, deeper, and more likely to leave a scar.

Symptoms

• A red, tender lump that grows over a few days to a week
• Pain and swelling
• A white or yellow head of pus
• Sometimes fever if large or multiple
• Eventually the boil usually "points" and drains on its own

Home care

• Warm compresses — apply a clean warm cloth for 10-15 minutes, 3-4 times a day. This is the most helpful self-care step — encourages the boil to come to a head and drain.
• Keep the area clean
• Don't squeeze or pop — forcing a boil can spread the infection deeper
• Cover with a clean dressing after it drains
• Wash hands after touching the boil
• Don't share towels, clothing, or razors with others

When to see a doctor

• A boil larger than about 2 cm
• Severe pain
• Fever
• Red streaks spreading from the boil (sign of cellulitis)
• Boil on the face (especially the nose or upper lip) — the facial "danger triangle" drains to the brain's venous system and can cause serious complications
• Boils that keep coming back
• Diabetes, weak immunity, or other conditions that make infections riskier

Doctors may lance (incise and drain) a boil that hasn't drained on its own. Antibiotics may be prescribed for large, severe, or facial boils, or when cellulitis is present. For recurrent boils, swabs may be taken to look for antibiotic-resistant bacteria, and decolonisation treatment (nasal antibiotic ointment, antiseptic body wash) may be advised.