What are boils?

Boils are pus-filled bumps on your skin. They develop when a hair follicle and the tissue around it become infected. Boils can be small, large, individual, or clustered.
Boils can be painful, cause discomfort, grow larger, and cause serious health complications if left untreated. Generally, boil treatment is simple, but it is better left to a doctor if boils are large, deep, and painful. It’s important to know how to identify a boil and what to do if you have one.
It’s also essential to know when to call the doctor so that you can keep boils from getting worse or causing other health problems.
Symptoms of boils
Boils begin forming as painful, red bumps under the skin. As they develop, you might experience any of the following symptoms:
Types of boils
Generally, there are two types of boils — the furuncle and the carbuncle. A furuncle occurs when an infection forms around a single hair follicle. Furuncles are larger than pimples and are more painful and warm.
If more than one hair follicle — called a cluster — becomes infected in the same area, the boil becomes a carbuncle.
If you have a weakened immune system, you might experience boils that keep coming back or occur in several places at once. This is called furunculosis.
Causes of boils
Your skin is covered with bacteria and viruses that are good and bad. Staphylococcus aureus (staph) is one of the most common forms of bacteria on your body and is one of the leading causes of boils.
Hair follicles are structures in the skin that hair grows out of. Scratches, small nicks in the skin, popping a pimple, or even bug bites create openings for bacteria to enter a follicle. This starts an infection, and the boil begins to grow as pus forms.
Other factors can make some people more likely to experience boils on their butt, including:
- A weakened immune system from other health conditions such as diabetes or cancer
- Conjunctivitis, eczema, or allergic asthma
Bacteria thrive in warm, moist conditions. People who are overweight can have skin folds, which are likely areas for bacteria to grow and cause boils.

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Eczema Browse our medical image collection of allergic skin disorders such as psoriasis and dermatitis and more caused by allergies See ImagesWhen to see the doctor for a boil
If you’ve got a boil on your butt, you’ll need to closely monitor it to make sure it isn’t growing larger or developing red streaks. If the boil grows, becomes streaked, or makes sitting too painful, you need to see your doctor immediately.
Some boils will go away on their own. However, if a boil lasts more than a week, contact your doctor. You should also contact your doctor or visit the emergency room in any of the following circumstances:
- If boils develop on your face, throat, neck, or spine
- If a fever accompanies the boil
- If a boil is painful enough to affect your daily life
Diagnosing boils
You can diagnose a boil by looking for the symptoms discussed above. If you’re unsure, your doctor will be able to diagnose it with a physical examination.
If you keep getting boils, your doctor may do blood tests to see if you have diabetes or another physical condition that makes you prone to developing boils.
Treating boils
Treating a boil is straightforward — hold a warm, wet washcloth over it for 20 to 30 minutes up to four times a day. The warmth helps your pores open and softens your skin, which allows pus to drain out of the boil. Do not try to cut open or squeeze the boil. Continue to use warm compresses as needed.
If the washcloth technique does not work within one week, call your doctor. They will likely create a small incision in the boil to drain it, and then pack it with gauze to absorb the pus. Your doctor might also give you antibiotics or other medical treatments to reduce the chances of further infection.
Preventing boils
There are some things you can do to lower your chances of developing a boil. Ensure you keep the areas of your body prone to boils clean and dry by washing with antibacterial soap and drying thoroughly.
If you see red bumps or skin irritations, don’t pick at them and use warm compresses to drain them. If you shave, don’t shave areas with pimples or other pus-filled follicles because this can spread bacteria to other places.
MedlinePlus: "Boils."
Michigan Medicine: "Folliculitis."
National Health Service: "Boils."
Nature Reviews Microbiology: "The skin microbiome."
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