A boil is an infected lump under your skin that is raised, red, painful, and filled with pus. Pus is a thick fluid that usually contains white blood cells, dead tissue, and germs such as bacteria or fungus. A carbuncle is a single area of infection formed from a group of boils that develop close together due to spreading infection.
What is the cause?
Boils commonly develop because bacteria get into hair follicles, which are the small openings in your skin that hair grows from. Bacteria normally live on the skin, particularly on certain parts of the body, such as the nose, mouth, genitals, and rectum. The bacteria can cause an infection if they enter the skin through a scrape, irritation, or injury of some kind. Sometimes friction on the skin–from clothing, for example–will cause a hair follicle to swell up. This can make the opening to swell closed, trapping the bacteria inside and starting an infection.
Boils and carbuncles often form in moist areas of the body such as the back of the neck, buttocks, thighs, groin, and armpits. They also form where there are skin folds, such as the abdomen.
Boils and carbuncles are more common and may be harder to treat in people who have diabetes or poor circulation, and in people whose immune systems are weakened by HIV, cancer, or other health problems.
What are the symptoms?
Symptoms may include:
Swelling, redness, and warmth in the area of the boil or carbuncle
Rounded, raised â€œheadâ€ like a pimple
Drainage of pus or other fluid
Pain when you touch it or pain all of the time
You may have swollen lymph nodes if the boil is in your neck, armpit, or groin area. The lymph system is part of your body’s system for fighting infection. The lymph system consists of lymph nodes that store blood cells (lymphocytes) to fight infection and vessels that carry fluid, nutrients, and wastes between your body and your bloodstream.
How are they diagnosed?
Your healthcare provider will ask about your symptoms and medical history and examine you.
If you have boils often, you may have lab tests of your blood or urine. These tests can check for conditions such as diabetes or kidney or liver disease that might make you more likely to have the boils.
How are they treated?
A boil can sometimes be treated at home, but a carbuncle often needs medical treatment.
For treatment at home, you can:
Wash your hands and then put a warm, moist cloth on the boil or carbuncle for 10 to 15 minutes at least 3 times a day. This improves blood flow and helps the boil drain on its own. Once the boil begins to drain, you will have less pressure and pain.
If the boil or carbuncle is in your groin or on your buttock you can soak in a tub of warm water for 10 to 15 minutes. Be sure to clean the tub well before and after soaking so that infection is not passed to others.
After soaking or using the moist cloth, clean the skin around the sore with water and antibacterial soap. Put a sterile gauze bandage over the area until it is healed. Replace it every day. If drainage soaks through the bandage or the bandage gets wet or dirty, change it as soon as possible. Wash your hands before and after you change the bandage.
Take a nonprescription pain medicine as needed. Follow the label directions.
These steps will help relieve the pain, reduce the risk of spreading the infection, and help boils to heal.
Sometimes your healthcare provider will need to drain the boil. To do this, your healthcare provider will clean the skin over the boil and may inject medicine to make it numb. Your provider will use a needle or cut the skin over the boil and drain it. Draining the pus often decreases the pain right away because it relieves the pressure. Your healthcare provider may pack the pocket with gauze, and leave some gauze sticking out through the cut in your skin. This lets any pus that forms in the boil drain out. The gauze packing is changed every day or two until the boil heals.
If a boil doesnâ€™t yet have a point or head on it, your provider may prescribe an antibiotic to see if it will get rid of the boil without draining or opening of the boil.
In most cases, a boil will not heal until it opens and drains. The time it takes for a boil or carbuncle to heal depends on how big it is and what other health problems you have. Most boils or carbuncles heal in 1 to 3 weeks.
How can I take care of myself?
Follow the full course of treatment prescribed by your healthcare provider. Take pain or antibiotic medicine exactly as prescribed by your healthcare provider. If you are given an antibiotic, take it for as long as your healthcare provider prescribes, even if you feel better. If you stop taking the medicine too soon, you may not kill all of the bacteria and the infection may come back.
Ask your healthcare provider:
How long it will take to recover
If there are activities you should avoid and when you can return to your normal activities
How to take care of yourself at home
What symptoms or problems you should watch for and what to do if you have them
Make sure you know when you should come back for a checkup.
To help prevent boils and carbuncles from spreading and coming back:
Do not open or squeeze the boil or carbuncle yourself. This can spread the infection.
If the boil opens or drains, clean it with an antibacterial soap. Cover it with a loose, gauze bandage. Change the bandage at least every day until the boil stops draining.
Wash your hands often with soap for at least 15 seconds. Always wash your hands after caring for the boil, after using the bathroom, and especially before touching any food. (The bacteria that cause boils can also cause food poisoning.) You can also carry an alcohol-based hand cleaner to clean your hands when soap and water arenâ€™t available.
Wash clothes that touch the infected area in hot, soapy water. Dry clothes on the hot setting if you use an automatic dryer.
Contact your healthcare provider if you have new or worsening symptoms.
What can I do to help prevent boils and carbuncles?
Bathe or shower daily.
Donâ€™t share washcloths, towels, clothing, bath water, or razors. Sharing these items could spread the bacteria that causes boils.
Avoid tight clothing that can irritate skin and hair follicles and cause a boil or carbuncle.
Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth. Last modified: 2014-07-08 Last reviewed: 2014-07-10
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.