The Bottom Line

A boil (furuncle) is a painful, pus-filled lump caused by a bacterial infection deep in a hair follicle. Carbuncles are clusters of boils with multiple openings — they are more serious and almost always need medical treatment. About 6–12% of people develop a boil at some point in their lives. Most single boils can be managed with warm compresses, but larger infections often require drainage and antibiotics from a doctor.

What Are Boils and Carbuncles?

A boil (also called a furuncle) is a painful, swollen lump filled with pus that forms around a hair follicle deep in the skin. It starts as a tender red bump and grows larger over days as pus collects inside. Eventually, many boils come to a head and drain on their own.

A carbuncle is a more serious infection — it's a cluster of connected boils that form a large, deep lump with multiple openings that drain pus. Carbuncles develop in about 5% of people who get boils and are more likely to cause fever, fatigue, and other signs of illness.

Both conditions are almost always caused by Staphylococcus aureus bacteria, which accounts for 75–85% of cases. MRSA (a drug-resistant staph) is involved in about 5–10% of cases and is more common in people who have recently taken antibiotics or have had repeated infections.

Signs and Symptoms

Boil (furuncle):

  • Tender, red, round lump starting at a hair follicle
  • Grows over several days, often to the size of a pea or grape
  • Center becomes yellow or white as pus forms
  • May drain spontaneously
  • Common locations: face, neck, armpits, buttocks, thighs

Carbuncle:

  • Larger, deeper mass connecting multiple boils
  • Multiple pus-draining openings on the surface
  • Fever, chills, fatigue, and swollen lymph nodes may occur
  • Heals more slowly and may leave a scar

What Causes Boils?

Staphylococcus aureus bacteria enter the skin through small cuts, abrasions, or clogged hair follicles. The body's immune system fights back, and the resulting battle between bacteria and white blood cells creates pus and the characteristic swelling.

Risk factors include:

  • Diabetes mellitus (2–3 times higher risk)
  • Obesity (increased friction and skin folds)
  • Weakened immune system (HIV, chemotherapy, immune-suppressing medications)
  • Close contact with someone who has active boils
  • Nasal carrier of Staph aureus (present in about 30% of the general population)
  • Poor hygiene or shared towels and clothing

About 10–15% of people who get boils will have recurring episodes. Persistent nasal Staph carriage is the leading risk factor for recurrence.

Treatment Options

  • Warm compresses: For small boils, apply a warm, moist cloth for 10–15 minutes several times a day. This brings the boil to a head and helps it drain naturally. Do not squeeze or pop a boil — this can spread infection deeper.
  • Incision and drainage (I&D): For larger boils and all carbuncles, a doctor numbs the area and makes a small cut to drain the pus. This is the most effective treatment and provides quick relief.
  • Antibiotics: Not always needed for a single small boil, but often prescribed for carbuncles, boils with spreading redness, signs of systemic illness, or boils in people with diabetes or weakened immune systems. Oral antibiotics (trimethoprim-sulfamethoxazole, doxycycline, or clindamycin) are commonly used.
  • Decolonization for recurrent infections: If you keep getting boils, your doctor may recommend nasal mupirocin ointment and chlorhexidine body washes to reduce Staph bacteria on your skin and in your nose.

When to See a Dermatologist or Doctor

  • The boil is on your face, especially near your nose or eyes
  • The boil is larger than about 2 cm or keeps growing rapidly
  • You have a carbuncle (cluster of boils)
  • You have fever, chills, or feel generally unwell
  • You are diabetic or have a weakened immune system
  • You are having recurring boils (3 or more per year)
  • The boil does not improve after a week of warm compress treatment

Frequently Asked Questions

Can I pop a boil at home?

No — you should not pop or squeeze a boil. Doing so can push the infection deeper into the skin or spread bacteria to surrounding tissue. Warm compresses help the boil drain naturally. If it needs draining, a doctor should do it under sterile conditions.

Are boils contagious?

The bacteria that cause boils can spread through direct skin contact and by sharing towels, clothing, or other personal items. If you have an active boil, cover it with a clean dressing, wash your hands frequently, and avoid sharing personal items.

Why do I keep getting boils?

Recurrent boils often occur because Staphylococcus aureus bacteria live in your nose (nasal carriage) and keep reinfecting your skin. A doctor can test for this and prescribe a decolonization regimen — special nasal ointment and antiseptic washes — that significantly reduces recurrence rates.

Is a carbuncle dangerous?

Carbuncles are more serious than individual boils. They can cause fever and systemic illness, and in rare cases — especially in people with diabetes or a weakened immune system — bacteria can spread into the bloodstream. A carbuncle always needs medical evaluation and usually requires drainage and antibiotics.

References

  1. Dryden MS. Skin and soft tissue infection: microbiology and epidemiology. Int J Antimicrob Agents. 2009;34(Suppl 1):S2-S7.
  2. Stevens DL, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the IDSA. Clin Infect Dis. 2014;59(2):e10-e52.
  3. Daum RS. Skin and soft-tissue infections caused by methicillin-resistant Staphylococcus aureus. N Engl J Med. 2007;357(4):380-390.

Trusted Resources

Always consult a board-certified dermatologist for personalized advice about your skin condition and treatment options.