Boils and carbuncles

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

Hidradenitis suppurativa

Hidradenitis suppurativa, also known as acne inversa, is a chronic skin disease characterized by recurrent boil-like lumps (nodules) under the skin. The nodules become inflamed and painful. They tend to break open (rupture), causing abscesses that drain fluid and pus. As the abscesses heal, they produce significant scarring of the skin.

The signs and symptoms of hidradenitis suppurativa typically appear after puberty, usually in a person’s teens or twenties, although they can begin earlier in puberty, particularly in affected females. Nodules are most likely to form in the armpits and groin. They may also develop around the anus, on the buttocks, or under the breasts. In some cases, nodules appear in other areas, such as the nape of the neck, waist, and inner thighs.

The recurrent nodules and abscesses cause chronic pain and can lead to self-consciousness, social isolation, and depression. Rarely, long-term (chronic) abscesses on the buttocks can develop into a type of skin cancer called squamous cell carcinoma .

Frequency

Hidradenitis suppurativa was once thought to be a rare condition because only the most severe cases were reported. However, recent studies have shown that the condition affects at least 1 in 100 people when milder cases are also considered. For reasons that are unclear, women are more commonly affected than men.

Causes

In most cases, the cause of hidradenitis suppurativa is unknown. The condition probably results from a combination of genetic and environmental factors. Originally, researchers believed that the disorder was caused by the blockage (occlusion) of specialized sweat glands called apocrine glands. However, recent studies have shown that the condition actually begins with a blockage of hair follicles in areas of the body that also contain a high concentration of apocrine glands (such as the armpits and groin). The hair follicles have a buildup of a fibrous protein called keratin (hyperkeratosis). The blocked hair follicles trap bacteria, leading to inflammation and rupture. Researchers have several ideas about what initially causes the follicles to become blocked and why the nodules tend to recur, but the causes remain unclear.

Genetic factors clearly play a role in causing hidradenitis suppurativa. Some cases have been found to result from variants (also known as mutations) in the NCSTN, PSEN1, or PSENEN gene. The proteins produced from these genes are all components of a complex called gamma- (γ-) secretase. This complex cuts apart (cleaves) many different proteins, which is an important step in several chemical signaling pathways. One of these pathways, known as Notch signaling, is essential for the normal growth and maturation (differentiation) of hair follicle cells and other types of skin cells. Notch signaling is also involved in normal immune system function. Studies suggest that variants in the NCSTN, PSEN1, or PSENEN gene impair Notch signaling in hair follicles. Although little is known about the mechanism, abnormal Notch signaling appears to promote the development of nodules and lead to inflammation in the skin. Researchers are working to determine whether additional genes, particularly those that provide instructions for making other γ-secretase components, are also associated with hidradenitis suppurativa.

Researchers have studied many other possible risk factors for hidradenitis suppurativa. Obesity and smoking both appear to increase the risk of the disorder, and obesity is also associated with increased severity of signs and symptoms in affected individuals. Studies suggest that neither abnormal immune system function nor hormonal factors play a key role in causing the disease. Other factors that were mistakenly thought to be associated with this condition include poor hygiene, the use of underarm deodorants and antiperspirants, and shaving or the use of depilatory products to remove hair.

Learn more about the genes associated with Hidradenitis suppurativa

Inheritance

Hidradenitis suppurativa has been reported to run in families. Studies have found that 30 to 40 percent of affected individuals have at least one family member with the disorder. However, this finding may be an underestimate because affected individuals do not always tell their family members that they have the condition, and hidradenitis suppurativa is sometimes misdiagnosed as other skin disorders.

In some families, including those with an NCSTN, PSEN1, or PSENEN gene variant, hidradenitis suppurativa appears to have an autosomal dominant pattern of inheritance. Autosomal dominant inheritance means one copy of an altered gene in each cell is sufficient to cause the disorder. In many cases, an affected person inherits the altered gene from a parent who has the condition.

Other Names for This Condition

• Acne inversa
• Apocrinitis
• Hidradenitides, suppurative
• Hidradenitis, suppurative
• Suppurative hidradenitides
• Suppurative hidradenitis

Boils and carbuncles

Boils and carbuncles are red, painful lumps that form just under the surface of the skin. They are usually caused by a bacterial infection.

Boils

Boils can develop anywhere on your skin. But you’re most likely to get a boil in an area where there’s a combination of hair, sweat and friction, such as the face, neck, armpits or thighs.

A boil on the back of the hand

Over time, pus forms inside the boil, making it bigger and more painful. Most boils eventually burst. The pus then drains away without leaving a scar. This can take from two days to three weeks to happen.

It can sometimes be difficult to tell the difference between a boil and a spot. But boils tend to grow bigger and become more painful. Your GP should be able to diagnose a boil from its appearance.

Carbuncles

A carbuncle is a dome-shaped cluster of boils. It usually develops over a few days. The areas most commonly affected are the back, thighs, or back of the neck.

A carbuncle is a dome-shaped cluster of boils

A carbuncle can grow to a size of 3-10cm and will leak pus from a number of points.

• have a high temperature of 38C (100.4F) or above
• feel generally unwell
• feel weak and exhausted

Carbuncles are less common than boils. They tend to mostly affect middle-aged or older men in poor health or with a weakened immune system. Boils are common in adolescents and young adults.

When to see your GP

See your GP if you think you have a carbuncle.

With boils, you don’t usually need to see a doctor as most boils burst and heal by themselves. But see your GP 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 – it may not burst and heal by itself
• that doesn’t heal within two weeks
• and you have a temperature and feel generally unwell

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

Treating boils and carbuncles

Self care

Most boils get better without the need for medical treatment.

One of the best ways to speed up healing is to apply a warm, moist face cloth to the boil for 10-20 minutes, three or four times a day.

Be careful not to use water that’s too hot. Make sure the face cloth is not too warm to avoid a scald or burn. Test how warm it is using the skin on the back of your hand.

The heat increases the amount of blood circulating around the boil. This sends more infection-fighting white blood cells to the area.

When the boil bursts, cover it with sterile gauze or a dressing. This is to prevent the spread of infection.

Afterwards, wash your hands thoroughly using hot water and soap.

Never squeeze or pierce a boil because it could spread the infection.

You can use over-the-counter painkillers, such as paracetamol or ibuprofen, to help relieve any pain caused by the boil.

Draining boils

If your boil doesn’t heal, your GP may decide to drain it, or refer you to hospital to have this done. They’ll usually numb the area first and then use a sterile needle or scalpel to pierce the boil.

Antibiotics

Antibiotics are usually recommended:

• for all cases of carbuncles
• if you have a high temperature
• if you develop a secondary infection, such as cellulitis (infection of the deeper layers of the skin)
• if you have a boil on your face – facial boils have a higher risk of causing complications
• if you’re in severe pain and discomfort

It’s very important to finish the course of antibiotics even if the boil goes away. If you don’t the infection could return.

Treating recurrent boils and carbuncles

You’re likely to need further treatment if you keep getting boils or carbuncles.

Most people who keep getting boils are carriers of Staphylococcus aureus (staph bacteria). This means they have staph bacteria living on their skin or inside their nose.

Treatment will depend on where the bacteria are found on your body. Your GP will advise you about treatment.

Causes of boils and carbuncles

Boils and carbuncles are often caused by a type of bacteria called Staphylococcus aureus (staph bacteria) that infects one or more hair follicles.

You can get a boil when bacteria enter the skin through cuts and grazes.

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

Complications of boils and carbuncles

Although most boils and carbuncles don’t cause further problems, some people develop a secondary infection.

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

Larger boils and carbuncles can also lead to scarring.

Preventing boils and carbuncles

You can’t always avoid getting a boil or carbuncle, but these simple steps can reduce your risk:

• wash your skin regularly using a mild antibacterial soap
• carefully clean any cuts, wounds or grazes (even small ones)
• cover cuts, wounds and grazes with a sterile bandage until they heal
• eat healthily and exercise regularly to boost your immune system

Catching boils or carbuncles

You can catch a boil or carbuncle. Unlike acne, boils and carbuncles can spread to another part of the body or to another person.

To prevent boils and carbuncles spreading, take simple precautions such as:

• washing your hands after touching affected areas
• using a separate face cloth and towel
• washing underwear, bed linen and towels at a high temperature
• covering wounds with a dressing until they heal
• carefully disposing of used dressings

More useful links

The information on this page has been adapted from original content from the NHS website.

For further information see terms and conditions.

Health conditions A to Z

Or find conditions beginning with A to Z …