A boil is a pocket of pus around a hair root.
Germs, usually a bacterium called Staphylococcus that lives harmlessly on many people’s skin, get into a hair root through a small break in the skin. White cells rush in to fight them, and pus collects: a red, hot, tender lump that comes to a yellow head. Most small boils burst and heal on their own within one to two weeks.
In plain words.
Boils are common in hot, humid weather, with sweat and rubbing, in people with diabetes, in those who are overweight, and when someone else in the family has them. A cluster of boils joined together, often on the back of the neck, is called a carbuncle; it needs a doctor.
Cellulitis is an infection spreading through the deeper skin, rather than a pocket of pus: a red, hot, swollen, painful area that grows over hours to days, most often on a leg. It often starts from a crack between the toes, a cut or an insect bite. It needs antibiotic tablets, and sometimes a drip in hospital.
Boils that keep coming back are worth a check for diabetes, and sometimes for carrying the germ in the nose. A doctor can plan a short course of nose ointment and body washes to clear it, often for the whole family.
How a boil forms
Germs live on everyone’s skin. Beside each hair lies a small oil gland. A cut, a scratch or rubbing gives germs a way down into the hair root.
Germs multiply in the hair root. White cells rush in from the blood to fight them, and pus collects in a pocket that pushes up a red, hot, painful lump with a yellow head.
Sometimes the infection spreads beyond the pocket: the redness widens, a red streak may run from it, and fever follows. This needs a doctor the same day.
Go to hospital now if
- A skin infection with fever and shivering, or feeling faint, confused or very unwell: go to hospital now.
- Redness spreading so fast you can see it grow within hours, skin turning dark, purple or blistered, or pain far worse than the skin looks: go to hospital now.
- A boil or swelling on the face, near the nose or eyes, with fever, headache or a swollen eye: go to hospital now.
- Diabetes, with a red, swollen, painful foot or an infected foot wound: go to hospital now.
Call 112 or go to the nearest emergency department. Ambulance: 108 (102 in some states).
See a doctor within a day if
- Redness is spreading around a boil, or a red line runs from it
- A boil wider than about 5 cm, or several joined together
- A boil on the face, in the armpit or groin, or near the back passage
- You have diabetes, kidney disease, or a weak immune system
- A boil is not better after a week, or boils keep coming back
Tests that help.
Not everyone needs every test. He decides which ones are worth doing for you.
| Test | What it tells |
|---|---|
| Blood sugar and HbA1c | Diabetes makes boils more likely and slower to heal, and is often found this way. |
| Pus culture and sensitivity | For boils that are drained, keep coming back, or do not settle: names the germ and the antibiotics that work on it. |
| Blood count and CRP | For fever or a spreading infection. |
| Kidney function (creatinine) | Before some antibiotics, and in anyone unwell. |
| Ultrasound of the swelling | Shows whether a lump holds pus that needs draining. |
Have it ready.
Tick them off as you gather them. The ticks stay on this phone only.
Online, or in person?
Do not squeeze a boil, especially on the face, and do not prick it with a needle at home. Antibiotics are not needed for most small boils, and a large boil needs draining, not only tablets.
A video call can
- Tell a simple boil from one that needs draining or antibiotics
- Watch spreading redness with photos over a day or two
- Choose an antibiotic when one is needed, and check for diabetes
- Plan how to stop boils coming back
Needs a visit in person
- Draining a boil: a small cut by a doctor, under local anaesthetic
- Antibiotics by drip for a spreading infection with fever
- Blood tests and pus culture
- Any sign in the red box: that is an emergency
Talk it through with Dr. Arya.
Bring your reports and medicines to a video consultation. He goes through them with you, in plain words, and says clearly if you need to be seen in person.
Book a video consultationDr. Prabhat Arya · MBBS, MD (Internal Medicine) · Delhi Medical Council Reg. No. DMC-83759