A boil is a swollen, red lump under the skin that can become pus-filled over time. It is often sore and painful, but usually clears up on its own.
Studies show that the average boil bursts after 2 to 3 days (although it can take up to a week or more), so it’s best to let the healing process happen naturally.
Knowing what to expect from a boil is key to knowing when to care for a boil yourself and when to get it checked by a doctor.
A boil often starts as a tender or itchy spot surrounding a hair follicle. As the affected area starts to fill with pus, the boil grows and forms a firm, red lump under your skin.
Boils often look like large pimples, and most grow to be the size of a pea.
After several days or weeks, the boil will usually form a whitish head and then burst, allowing the pus to drain away. Some boils may settle slowly without bursting.
Most small to medium-sized boils don’t cause permanent scarring, but larger boils may leave a scar.
A boil should burst and heal on its own, without the need to see a doctor. However, you should see a doctor if:
A boil is usually caused by an infection, and the above symptoms can be a sign that the infection has spread to the surrounding skin (cellulitis).
If you have a boil on your face, nose or spine, it’s best to see a doctor. A boil that forms in these places can lead to complications and a doctor may want to drain it before the infection has a chance to spread.
You should see a doctor if a boil keeps coming back. They may want to run some tests to work out why you keep getting a boil.
A doctor may also want to rule out some health problems that can increase your chance of getting a boil, such as type-2 diabetes or a weakened immune system.
A carbuncle is a group of boils that develop next to each other and join beneath the skin. Carbuncles are generally 3 to 10cm in size and often leak pus from multiple points.
They can be very painful and may cause serious complications if left untreated. If you think you have a carbuncle, visit a doctor.
You can usually treat a boil yourself with simple remedies like a warm compress to ease symptoms and encourage healing. Get started by reading this article on treating boils at home.
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Boils and carbuncles [Internet]. nhs.uk. 2020 [cited 22 January 2020]. Available here.
Complications of boils and carbuncles - HSE.ie [Internet]. HSE.ie. 2020 [cited 22 January 2020]. Available here.
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Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.