Causes and Risk Factors of Carbuncles

Learn more about this collection of infected hair follicles

Carbuncle on elbow

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In This Article

A carbuncle is a collection of multiple infected hair follicles. The infection is typically caused by Staphylococcus but it can be caused by other bacteria. Carbuncles are more common in those who have a weakened immune system or who have a chronically broken skin barrier.

Common Causes

A carbuncle is a type of skin abscess. Like a furuncle (AKA boil) carbuncles develop when the hair follicle becomes infected. A carbuncle is a much more serious infection, though.

A furuncle is an infection of a single hair follicle and its surrounding tissue, while a carbuncle is actually several furuncles that are densely packed together.

Carbuncles generally begin as furuncles. As the infection spreads it affects other follicles and extends into the deeper layers of the skin—the subcutaneous fat. The infected mass develops several heads of pus.

Carbuncles tend to occur in areas with thicker skin like the nape of the neck, the back, or the thighs.

If you think that you may have a carbuncle, call your primary care provider or a dermatologist (a doctor who specializes in treating the skin).

Staphylococcus

While other bacteria are sometimes responsible, the vast majority of carbuncles are caused by Staphylococcus aureus, or staph, infection.

Staph is a very common bacteria often found on the skin, inside of the nose, and in the genital area, of human beings. In the majority of cases, it's harmless.

The problem develops when the bacterium enters the skin through a broken area. Here, the bacteria proliferate, infecting several follicles and coalescing into a mass of infected tissue and pus.

There doesn't have to be a large injury for the infection to take hold. In some cases, it could be a simple scratch, scrape, or insect bite. Even a small microtear in the skin, so small you can't see it, allows the infection to take hold.

Friction also plays a role in carbuncle development. Friction can lead to irritation and inflammation of the hair follicle (folliculitis). The infection can more easily take hold withing the inflamed hair follicle.

Methicilin-Resistant Staphylococcus Aureus (MRSA)

Over the past several years, there has been a sharp increase in the incidence of infections caused by a special strain of Staphylococcus aureus that is resistant to the normal penicillin-based antibiotic treatment.

Until recently, methicillin-resistant Staphylococcus aureus (MRSA) was an uncommon bacterial strain that occurred in nursing homes and other long-term care facilities. But with the overuse of antibiotics for conditions that don't require antibiotics, MRSA infections are now, unfortunately, common in certain regions of the United States.

MRSA is becoming a fairly common cause of carbuncles, especially recurrent carbuncles.

These infections often occur spontaneously in the groin, buttock, and upper thigh region.

Health Risk Factors and Genetics

Carbuncles can affect anyone at any age, but certain factors put you at elevated risk for developing carbuncles.

  • Being male: Men are more likely to develop carbuncles, as well as furuncles. Carbuncles affect middle-aged and older men more often, while furuncles are more common in teenage boys and young adults.
  • Diabetes: Carbuncles are especially common in those with uncontrolled diabetes.
  • Chronic skin conditions: Chronic skin conditions that leave the skin's barrier compromised makes it easier for bacteria to enter and set up shop. This includes common conditions such as acne, folliculitis, eczema, and other types of dermatitis.
  • Being immunocompromised: Those with chronic infections, HIV, cancer, and other conditions that weaken the immune system puts you at greater risk for developing carbuncles. This is because the body has a harder time fighting off infection, allowing the bacteria to rapidly grow unchecked.
  • Certain medications: Taking certain medications that weaken the immune system. Along the same lines, medications that weaken the immune system also prevent your body from fighting carbuncle-causing infection efficiently. Examples include long-term oral steroid use or chemotherapy.
  • Having multiple or recurrent boils: Certain people are more susceptible to being infected by staph. Those who are prone to getting recurrent are more likely to develop more serious abscesses like carbuncles.
  • Other health conditions: Carbuncles are also more common in those with health conditions like heart failure, liver disease, and kidney disease.

Recurrent carbuncles may signify there is an undiagnosed health condition that is hindering your body's ability to fight off infection. In this case, your doctor will suggest further testing.

Lifestyle Risk Factors

Besides health conditions, there are several lifestyle factors that can make you more susceptible to developing carbuncles.

  • Close contact with a person who has a staph or MRSA infection: The bacteria that cause carbuncles are contagious. Living or caring for someone with a staph infection puts you at greater risk of developing one yourself. It's not unusual for several members of the same family to have furuncles or carbuncles at the same time.
  • Obesity: Being overweight makes one more susceptible to skin infections. This may be because bacteria thrive in moist environments such as skin folds, or that being overweight makes it harder to fight infection. The risk is highest in those with a BMI over 30.
  • Living in crowded quarters: Staph can run rampant in communal living places such as dorms and military barracks, where infections can easily pass from person to person and via surfaces. Homeless shelters and prisons are also prime places for the bacteria that cause carbuncles to spread.
  • Being an athlete: From sharing athletic equipment or personal effects in the locker room, to close-contact sports like wrestling, staph can also spread easily among athletes.
  • Poor hygiene: The bacteria that cause carbuncles is common, and can live almost anywhere. Good hygiene practices such as hand washing, showering, and laundry practices, help prevent infection. On the flip side, poor hygiene practices put you more at risk.
  • Injected drug use: According to a 2018 study, those who use injected drugs are 16 times more likely to develop serious MRSA infections. This includes both prescription and non-prescription drugs.

A Word From Verywell

Carbuncles are fairly common skin infections. They develop when several boils coalesce into a serious, deep abscess. Most carbuncles are caused by the Staphylococcus aureus bacterium. Carbuncles occur most often in middle-aged and older men, especially those who have health conditions such as diabetes and heart disease or weakened immune systems.

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Nowicka D, Grywalska E. Staphylococcus aureus and host immunity in recurrent furunculosis. Dermatology. 2019;235(4):295-305. doi:10.1159/000499184

  3. Creech CB, Al-Zubeidi DN, Fritz SA. Prevention of Recurrent Staphylococcal Skin Infections. Infect Dis Clin North Am. 2015 Sep; 29(3): 429–464. doi:10.1016/j.idc.2015.05.007

  4. Kaspersen KA, Pedersen OB, Petersen MS, et al. Obesity and risk of infection: results from the Danish Blood Donor Study. Epidemiology. 2015 Jul;26(4):580-9. doi:10.1097/EDE.0000000000000301

Additional Reading

  • Clebak KT, Malone MA. Skin Infections. Prim Care. 2018 Sep;45(3):433-454. doi:10.1016/j.pop.2018.05.004

  • Ibrahim F, Khan T, Pujalte GG. Bacterial Skin Infections. Prim Care. 2015 Dec;42(4):485-99. doi:10.1016/j.pop.2015.08.001

  • InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Boils and carbuncles: Overview. 2018 Jun 14.

  • Halpern, Analisa, and Warren Heymann. "Bacterial Diseases." Dermatology. 2nd. Ed. Jean Bolognia. New York: Mosby, 2008: 1075-84.