Boils, Carbuncles and Furunculosis


A boil (furuncle) is an infection of a hair follicle. It is usually caused by a bacterium called Staphylococcus aureus. A boil looks like a small red lump on the skin that is tender. The surrounding skin may be swollen and inflamed. Pus fills the centre of the boil.

A carbuncle occurs when a group of hair follicles next to each other become infected. It is like a multiple boil.

Chronic furunculosis is a condition where you have multiple boils that occur over a period of time. The boils can develop continuously, or occur from time to time.

Who gets boils and where do they develop?

Boils can develop in any hairy area of skin. In particular, in sites where there is friction, or where the skin is sweaty. For example, the neck, face, armpit, arms, buttocks and around the anus. Carbuncles most commonly develop on the back of the neck or on the thighs.

You have a higher risk of developing a boil or carbuncle if you have the following:

  • Skin conditions that may cause you to scratch and damage the skin - eczema or scabies.
  • Obesity.
  • A poor immune system.
  • An illness making you frail or generally unwell.
  • You are a carrier of staphylococcal bacteria

What is the treatment for a boil or carbuncle?

Small boils may subside and go without any treatment. You can ease pain by covering the boil with a soft cloth soaked in hot water. Do this for 30 minutes, 3-4 times a day.
Larger boils and carbuncles are best treated by letting the pus out. This is done by a doctor who drains the pus by a small cut in the skin (incision and drainage). The wound is covered with a dressing until the skin heals. The skin usually heals quickly once the pus has been drained.

A course of antibiotics is often prescribed in addition to draining the pus to help clear the infection from the skin.

What if they are not treated?

A boil may get larger and more tense and painful as more pus accumulates. Typically, after several days the boil will burst and pus will leak on to the skin. A scar may be left at the site of the boil.

A carbuncle tends to increase in size for a few days up to 3-10 centimeters across, sometimes more. After few days, various pus-filled lumps appear on the surface and pus leaks on to the skin. It then may break down and form an ulcer on the skin surface before the infection gradually subsides. The skin then gradually heals leaving a deep scar.

Whilst there is infection and pus in the skin, there is a risk that some bacteria may spread in the bloodstream to cause infections in other parts of the body.

Recurring boils (chronic furunculosis)

One cause of recurring is that you, or someone in your family or household, may be a carrier of staphylococcal bacteria. If you are a carrier you tend to be more prone to skin infections and boils. In particular, these bacteria may quickly invade and multiply in broken skin following a minor cut or injury. Treatment with antibiotics and/or antibiotic nasal cream may clear staphylococcal bacteria from carriers and reduce the chance of boils, or other types of skin infection, from recurring


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