Boils (Furuncles and Carbuncles)

What a boil looks like

• starts as a red, tender, pea-sized lump
• grows over a few days and becomes more painful
• skin around it becomes red, warm and swollen
• a yellow or white tip (head) forms as pus collects
• it may burst and drain pus, then pain eases quickly

A carbuncle is a group of boils joined under the skin, often on the back of the neck, shoulders or thighs. It is deeper, more painful, drains from several openings, and is more likely to cause fever and tiredness.

Boils vs other skin lumps

Causes and risk factors

Staphylococcus aureus lives harmlessly in the nose or on the skin of many people. It causes a boil when it enters a hair follicle through a small break in the skin from shaving, friction or scratching. MRSA, a strain resistant to some antibiotics, is a common cause in the community.

Risk is higher with:

• close contact with someone who has boils
• contact sports, shared gym equipment, military training or crowded living
• sharing towels or razors
• friction from tight clothing
• diabetes and a weakened immune system
• eczema and other skin conditions that break the skin barrier
• obesity
• being a staph carrier in the nose

Diagnosis

Boils are diagnosed by appearance. A swab of the pus may be sent to the lab to identify the bacteria and check for MRSA, especially for recurrent or severe boils. Blood tests check for diabetes or spreading infection when needed.

Treatment

Home care for small boils

1. Warm compresses: apply a warm, damp cloth for 10 to 15 minutes, 3 to 4 times a day. Heat helps the boil come to a head and drain naturally.
2. Do not squeeze, pop or cut it. This can push bacteria deeper and spread infection.
3. Once it drains, wash gently with soap and water and cover with a clean dressing. Change it daily or when soaked.
4. Wash your hands after touching the boil, and keep towels and clothing separate. Wash them in hot water.
5. Pain relief with acetaminophen (paracetamol) or ibuprofen, following the label dose.

Medical treatment

• Incision and drainage: a clinician numbs the skin, makes a small cut and drains the pus. This is the most effective treatment for larger boils and carbuncles.
• Antibiotics are added for large boils, carbuncles, surrounding cellulitis, fever, boils on the face, and for people with diabetes or weak immunity. Choice depends on the likelihood of MRSA.

Recurrent boils

Repeated boils are common, often because you carry staph in your nose or on your skin. A doctor may recommend a decolonization routine:

• an antibiotic ointment such as mupirocin inside the nostrils twice daily for 5 days
• daily antiseptic body washes, such as chlorhexidine, or dilute bleach baths
• treatment of household members at the same time
• washing bedding, towels and clothes in hot water

Your doctor may also check for diabetes and immune problems.

Complications

• cellulitis, a spreading skin infection
• an abscess that needs drainage
• scarring, especially with carbuncles
• rarely, spread of infection to the blood, bones, heart valves or, from the central face, to veins around the brain

Prevention

• Wash hands frequently.
• Keep cuts and scrapes clean and covered until healed.
• Do not share towels, razors, sports gear or clothing.
• Shower after contact sports or gym sessions.
• Manage diabetes and skin conditions such as eczema.

Frequently asked questions

What is the fastest way to get rid of a boil?

For a small boil, apply warm compresses several times a day to bring it to a head and let it drain on its own. For a large or very painful boil, a clinician can drain it in a few minutes, which gives fast relief. Do not squeeze it yourself.

What causes boils?

Boils are usually caused by Staphylococcus aureus bacteria infecting a hair follicle through a small break in the skin. Risk factors include close contact with someone with boils, shared towels or razors, friction, diabetes, a weak immune system and skin conditions such as eczema.

Are boils contagious?

The bacteria that cause boils can spread through direct skin contact or shared items such as towels, razors and sports equipment. Keep boils covered, wash your hands after touching them and launder towels and clothes in hot water.

Why do I keep getting boils?

Recurrent boils are usually due to carrying staph bacteria in your nose or on your skin. Diabetes, weakened immunity and hidradenitis suppurativa can also cause repeated lumps. A doctor can test you and recommend a decolonization routine.

When should a boil be drained by a doctor?

See a doctor if a boil is larger than about 2 cm, very painful, has not improved after a week of warm compresses, is on the face, spine or groin, or if you have fever or spreading redness. These boils usually need draining.