Boils and carbuncles

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at May 21, 2016
StartDiseasesBoils and carbuncles

Boils and carbuncles are both red bumps that form beneath the surface of the skin and then erupt on the skin's surface. They are two related but different conditions, with carbuncles being the more severe of the two. Both boils and carbuncles are filled with pus and sometimes painful because they are the physical symptoms of a bacterial infection, fungal infection, or an inflammation of hair follicles. Boils are also known as furuncles.


Definitions & Facts

Boils erupt on the skin, forming red lumps which fill with pus. They grow larger and usually become more painful as the pus builds up, until they finally rupture and the pus is able to drain out. Many boils are caused by the common bacteria, Staphylococcus aureus which is found on the surface of the skin and inside the nose. Boils often develop at spots on the body where the skin is broken by an insect sting or a small scratch or cut which give the bacteria an easy way to enter the body.

Carbuncles are often much larger than boils because they are comprised of a cluster of boils. Carbuncles can go deep into the body and cause more severe infection than boils; they are also far more likely to leave scars after they’ve healed. The severity of the infection can make people experience fever and chills or just feel generally unwell.

Symptoms & Complaints

Boils can occur anywhere on the body, but the most common places for them to appear are on the face, neck, buttocks, thighs, and under the arms; these are all areas that have hair, and are all at locations where people sweat or have friction.

Signs of a boil can include: a bump that is red and painful, that starts out pea-sized but will continue to get bigger; boils have been known to get to be the size of a baseball, but that is very unusual. The skin around the bump can become swollen, red, and painful or tender to the touch. A boil will develop a yellowish-white tip and that tip is what will release the pus to drain when the boil ruptures.

Carbuncles, which are most commonly seen on the back of the neck, the shoulders and the thighs, begin as painful red bumps just like boils. Carbuncles tend to be much larger than boils, and they can ooze and crust even while they are still developing.

Other symptoms of carbuncles can include fatigue, fever, and a general feeling of illness, depending on how severe the infection is. The lymph nodes in the neck, armpits and groin may swell as may the tissue that is directly around the carbuncle.


Anyone at any age can develop boils or carbuncles, even if they are perfectly healthy. Factors that increase one's risk include:

  • Diabetes
  • Liver disease
  • Kidney disease
  • A compromised immune system
  • Other skin conditions such as eczema or psoriasis damage the skin and make one more susceptible to bacteria getting in and causing boils or carbuncles.
  • Being in close proximity to someone with a Staph infection
  • Close living situations such as boot camps or college dorms where items like towels or clothes may be shared are environments where boils or carbuncles are more likely to occur than less crowded situations. Boils and carbuncles can be contagious, and the infection can spread from one person to another either by skin-to-skin contact or shared personal items.
  • Tight clothing that irritates the skin can cause boils or carbuncles to develop
  • Shaving can cause small scrapes on the face that allow bacteria to enter the body
  • Older age
  • Obesity
  • Inadequate hygiene

Diagnosis & Tests

Boils and carbuncles are red, inflamed and not easy to miss, and physicians can usually diagnose them just by the way they look. Like so many other diseases, many of the varieties of bacteria that cause boils and carbuncles have become resistant to standard antibiotic treatment, so the doctor might have to take a sample of the pus and send it to a lab for more extensive testing.

Treatment & Therapy

Most cases of small or simple boils can be successfully treated at home. Applying warm compresses to the site consistently will help relieve the pain and will promote drainage. After that, the area will usually begin to heal without medication.

Carbuncles and large boils may require more comprehensive treatment. The doctor may have to make an incision in the swollen skin in order to thoroughly drain the area, but in cases of deep infection, even this may not get all of the pus and infection out. In these cases the doctor may pack the infected area with sterile gauze to absorb the additional pus and stop the infection from spreading. Boils and especially carbuncles can be much deeper than what may be visible from the surface, and cleaning them can be tricky. Antibiotics are often prescribed to help heal the infection at the site.

It is important to not squeeze the boil or carbuncle and to not try to open it to try to drain it because this may spread the infection to other parts of the body. One should call a physician if the pain is severe, if the bump lasts over two weeks, or if there is a fever with it.

Prevention & Prophylaxis

Basic cleanliness is the most effective way of avoiding being infected and developing a boil or carbuncle. Hands should be washed with soap and hot water after treating a boil or a carbuncle. It is also important to promptly launder all clothing, towels, sheets and compresses that have come into contact with the infection.

It isn’t very common, but sometimes the bacteria from a carbuncle or boil can enter the bloodstream and spread the infection to other parts of the body. When an infection spreads this way it is referred to as sepsis and can be life-threatening. This must be caught and treated aggressively because sepsis can lead to infections anywhere in the body including the bones or the heart.