Boils - Complications of boils and carbuncles

Although most boils do not cause further problems, this is not always the case.

Scarring

Scarring can sometimes occur following a larger boil or carbuncle. These scars never disappear completely, but they do fade with time and become less noticeable.

If you're particularly concerned about scars, there are a number of treatment options, including:

corticosteroid injections, which can help flatten a raised scar
pressure dressings, which can help flatten and soften a scar
plastic surgery

However, it's unlikely that your local clinical commissioning group (CCG) will fund these treatments unless it can be shown your scars are causing you considerable psychological distress.

A simpler alternative is to use make-up to conceal any scars you have. Camouflage make-up specially designed for covering scars is available over the counter at pharmacies.

Spread of infection

The bacteria inside a boil or carbuncle can sometimes spread to other parts of the body and trigger a secondary infection.

Cellulitis is the most common secondary infection associated with boils and carbuncles. It is an infection of the deeper layers of the skin.

Less common secondary infections associated with boils and carbuncles include:

impetigo – a highly contagious skin infection that causes sores and blisters
septic arthritis – an infection of a joint
osteomyelitis – an infection that develops inside a bone
endocarditis – an infection of the inner layer of the heart
septicaemia – an infection of the blood
brain abscess – a collection of pus that develops inside the brain

Some of these less common secondary infections need to be treated with injections of antibiotics. In the case of septicaemia and brain abscess, admission to an intensive care unit (ICU) may be required.

Cavernous sinus thrombosis

Cavernous sinus thrombosis is a very rare but potentially life-threatening complication of a boil. It occurs when an infection triggers a blood clot in the spaces behind the eye socket. The clot begins to increase the pressure on the brain, causing symptoms such as:

a sharp and severe headache
swelling of the eyes
eye pain that's often severe

Without prompt treatment with antibiotics, cavernous sinus thrombosis can be fatal. However, it should be stressed that only 1 in every 2.5 million people in England will develop this complication in any given year.

Read more about cavernous sinus thrombosis.