Introduction 

Boils and carbuncles are red, painful lumps on the skin.

Boils

Boils (furuncles) can develop anywhere on your skin, but they're most likely to occur at the site of an infected hair follicle (hole from which a hair grows).

Boils most commonly develop on areas of skin where there's a combination of hair, sweat and friction, such as the neck, face or thighs.

Over time, pus forms inside the boil, causing it to grow larger and become more painful. In most cases, a boil will eventually burst and the pus will drain away without leaving a scar. This can take from two days to three weeks to happen.

Boils are more common in teenagers and young adults, especially in males. Young males living in overcrowded and possibly unhygienic conditions are particularly at risk.

Carbuncles

A carbuncle is a dome-shaped collection of boils that usually develops over the space of a few days. They most often occur on the back of the neck, back or thighs.

A fully grown carbuncle can be more than 10cm (4 inches) in size, and will leak pus from a number of points.

You may also have additional symptoms, such as:

  • a high temperature of 38ºC (100.4ºF) or above
  • a general feeling of being unwell
  • feeling weak and exhausted

Carbuncles are less common than boils and tend to occur mostly in middle-aged or older men in poor health or with a weakened immune system.

When to see your GP

Most boils burst and heal by themselves without the need for medical treatment. However, visit your GP for advice if you have a boil:

  • on your face, nose or spine – this can sometimes cause serious complications
  • that gets bigger and feels soft and spongy to touch (as it may not burst and heal by itself)
  • that doesn't heal within two weeks

You should also see your GP if you develop a carbuncle or if you have additional symptoms such as a high temperature or feeling generally unwell.

You GP should be able to identify a boil or carbuncle by looking at it.

Causes of boils and carbuncles

Boils and carbuncles are often caused by a type of bacteria known as Staphylococcus aureus (staph bacteria) infecting one or more hair follicles. Staph bacteria usually live harmlessly on the surface of the skin or in the lining of the nose.

Boils tend to occur when the bacteria enters the skin through cuts and grazes. This causes your immune system to respond by sending infection-fighting white blood cells to kill the bacteria.

Over time, a mix of dead bacteria, dead white blood cells and dead skin cells builds up inside the boil to form pus.

A carbuncle develops when the infection spreads further beneath the skin to create a cluster of boils.

Can I catch a boil or carbuncle?

Yes, you can. Unlike acne, both boils and carbuncles can spread to another part of the body or to another person.

Taking simple precautions, such as carefully disposing of used dressings and washing your hands after touching affected areas of skin, can help prevent boils and carbuncles from spreading.

Treating boils and carbuncles

Most boils can be treated at home. One of the best ways to speed up healing is to apply a warm facecloth to the boil three or four times a day.

If your boil doesn't heal, your GP may decide to drain it.

Never attempt to squeeze or pierce a boil or carbuncle because it could cause the infection to spread and may lead to complications (see below).

If you develop a carbuncle or there's a high risk of your boil causing complications, you may be prescribed a week-long course of antibiotics.

Further testing, such as taking a skin swab or a blood test, may be required if you have:

  • a boil or carbuncle that keeps returning or doesn't respond to treatment – it may be caused by bacteria other than staph bacteria, so an antiseptic solution may be prescribed
  • multiple boils or carbuncles
  • a weakened immune system caused by a condition such as diabetes, or if you're having a treatment such as chemotherapy

Read more about treating boils and carbuncles.

Complications

Although most boils get better without causing further problems, some people develop a secondary infection.

This can range from a relatively minor (though often very painful) infection of the deeper layer of the skin, such as cellulitis, to rarer and more serious infections, such as blood poisoning (sepsis).

Larger boils and carbuncles can also lead to scarring.

Complications are more likely to occur if boils and carbuncles aren't treated properly.

Read more about the possible complications of boils and carbuncles.

Page last reviewed: 30/01/2015

Next review due: 30/01/2017