Updated 16 October 2015


A boil is a painful, pus-filled lump under the skin, caused by bacterial infection.



A boil is a painful, pus-filled lump under the skin, caused by bacterial infection of a hair follicle.


Boils are common, and usually due to infection with staphylococcus bacteria (S. aureus or S. epidermidis) which normally live on the skin.

Factors predisposing to boil formation include:

- Damage to the hair follicle, like a nearby cut or scratch;

- Diabetes;

- Immune suppression;

- Poor hygiene;

- Malnutrition; or

- Acne or other existing skin problems.

Boils most commonly affect the face, neck, armpit, thighs or buttocks, but can occur in any hairy area pf the body. Hidradenitis suppurative is a condition of boils in the armpits, and this may be associated with the overuse of anti-perspirant deodorants. Several boils may cluster to form a carbuncle.


A boil starts suddenly as a painful bump, pink or red, with swelling and tenderness of the surrounding skin. The bump enlarges over a few days and becomes more painful. It then develops a small yellow-white tip (point) which soon ruptures, allowing the pus to drain out and relieving the pain. Complete healing may take up to two weeks, and scarring is unusual.

If the boil is severe or unusual, or if there are underlying risk factors, tests – such as for diabetes or HIV – may be done to identify the problem.


Boils usually heal by themselves, and do not need treatment.

If treatment is needed, your doctor may make a small cut in the tip to let the pus drain, and may prescribe antibiotics if the infection seems deep, or if the boils are recurrent.

Do not squeeze or try to cut the boil open at home – this will cause complications such as spread of the infection and scarring of the skin.


Some situations warrant consulting your doctor:

- A boil which grows very quickly and is very painful

- Boils which have not healed in two weeks, or have an accompanying fever.

- Any visible red streaks on the skin coming from the boil

- If you have any condition, or are using medication, causing immune suppression (like HIV, or cortisone)

- Recurrent boils

- If you have an abnormal or artificial heart valve


Spread of the bacterium into the blood may cause septicaemia. This is of particular danger to patients with abnormal heart valves or with artificial valves, in whom bacterial endocarditis can be fatal.

(Dr AG Hall, Health24, January 2008)


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