Skin abscess

A skin abscess is a painful lump under your skin that's filled with pus, usually caused by a bacterial infection. Some go away on their own, but larger or more troublesome ones often need treatment from a GP.

What causes a skin abscess?

A skin abscess forms when bacteria get under your skin, for example through a small cut, graze, or along a hair follicle. Your immune system sends white blood cells to fight the infection, and as they do, pus builds up in a cavity under your skin.

Most skin abscesses are caused by a type of bacteria called Staphylococcus aureus (S aureus), including a strain known as MRSA (methicillin-resistant S aureus), which can cause abscesses that keep coming back. Bacteria that normally live harmlessly on your skin can sometimes cause an infection this way.

You're more likely to get a skin abscess if you:

• Smoke
• Are living with obesity
• Have diabetes
• Are between 15 and 40 years old
• Have a skin condition or inflammation, such as eczema.

Are there different types of skin abscess?

Skin abscesses can form anywhere on your body, but some types are more common than others:

• Boils (furuncles and carbuncles) – the most common form, usually starting in a hair follicle or an area of infected skin.
• Pilonidal abscesses – form in the skin at the base of your spine, in the cleft between your buttocks.
• Abscesses around the anus (perianal abscesses) – one of the most common sites, often needing prompt treatment.
• Abscesses in the armpit or around the genitals.

The treatment for each is broadly similar, though abscesses in some areas, such as near the anus, may need closer follow-up.

How is a skin abscess diagnosed?

A skin abscess is usually diagnosed by a doctor or nurse examining the lump and asking about your symptoms, such as how long it's been there and whether you feel generally unwell. If you need treatment, a swab sample may be taken if the abscess does not respond to initial treatment in order to identify the exact type of bacteria causing the infection and to guide the next antibiotic choice.

How is a skin abscess treated?

A small abscess may burst and heal by itself, and a warm compress held against it for a few minutes, several times a day, can sometimes help it drain naturally.

Larger or more painful abscesses usually need to be drained by a healthcare professional. This involves a small procedure, under local anaesthetic, to make a cut in the skin and let the pus drain out. The wound is normally left open rather than stitched, so that any further pus can continue to drain, and dressings are changed regularly until it heals, which usually takes around 2–3 weeks. You may also be given antibiotics, particularly if the infection is severe or hasn't fully cleared once the pus has drained.

To help prevent a skin abscess coming back, wash your hands regularly, keep any cuts or wounds clean and covered, and avoid sharing towels, clothing, razors or toothbrushes, especially while you have an active infection.

When should you see a doctor?

See a GP if you have a lump that's getting bigger, has lasted more than 2 weeks, feels hard and doesn't move, or if you have a weakened immune system or a long-term condition such as diabetes. Also get it checked if the lump is in your breast.

Get an urgent GP appointment or call 111 if the lump is painful, red or hot, if you feel hot, cold or shivery, or if you notice swelling or redness spreading away from the lump (this may be harder to see on brown or black skin). After treatment, contact a healthcare professional again if you notice worsening pain, redness, fever, or if the wound isn't healing as expected.