• A boil, or skin abscess, is a collection of pus that forms in the skin.
  • Boils symptoms and signs include:
    • a firm reddened pea-sized bump,
    • tender, swollen skin surrounding the bump,
    • the bump may increase in size,
    • Pus-filled head on the bump, which may spontaneously drain, weep, or ooze
  • Antibiotics alone can be inadequate in treating abscesses. The primary treatments for boils include hot packs and draining (“lancing”) the abscess, but only when it is soft and ready to drain. Most of these skin conditions resolve on their own or with home remedies.
  • Suppose the individual has a fever or chronic diseases, such as cancer or diabetes, or is taking medications that suppress the immune system. In that case, they should contact a health care professional if a boil (abscess) or other skin infection develops.
  • There are several ways to reduce the likelihood of developing some forms of boils. Still, boils are not entirely preventable even with proper hygiene and skincare regimens.
  • The bacteria that cause boils are contagious, and skin infections can be spread from contact with a boil’s fluid.

Causes of Boils (Skin Abscesses)

There are many causes of boils. Some boils can be caused by ingrown hair. Others can form as the result of a splinter or other foreign material that has become lodged in the skin. Others boil, such as those of acne, are caused by plugged sweat glands that become infected. Often the exact cause of a boil cannot be determined.


The skin is an essential part of our immune defense against materials and microbes that are foreign to our bodies. Any break in the skin, such as a cut or scrape, can develop into an abscess should it become infected with bacteria.


  • Individuals who have ingrown hairs may experience a painful acne-like eruption after shaving.
  • The upper skin layers may dilate the small superficial blood vessels, which gives the skin a red or flushed appearance.
  • Pustules and rare abscesses may form on the ingrown hair sites due to the infection with common skin bacteria, such as Staphylococcus and Pseudomonas.

Symptoms & Signs of Boils

A boil is a localized infection in the skin that begins as a reddened, tender area. Over time, the area becomes firm, challenging, and increasingly tender. Eventually, the boil’s center softens and becomes filled with infection-fighting white blood cells from the bloodstream to eradicate the infection. This collection of white blood cells, bacteria, and proteins is known as pus. Finally, the pus “forms ahead,” which can be surgically opened or may spontaneously drain out through the surface of the skin. Pus enclosed within the tissue is referred to as an abscess. A boil is also referred to as a skin abscess. Boils can occur anywhere on the body, including the trunk, extremities, buttocks, groin, armpit, or other areas.



There are several different types of boils:

  • Furuncle or carbuncle: This is an abscess in the skin usually caused by an infection with the bacterium Staphylococcus aureus. A furuncle can have one or more openings onto the skin and may be associated with a fever or chills. The term furuncle is used to refer to a typical boil that occurs within a hair follicle. The term carbuncle is typically used to represent a more massive abscess that involves a group of hair follicles and involves a larger area than a furuncle. A carbuncle can form a hardened lump that can be felt in the skin. Having chronic, recurrent boils (furuncles or carbuncles) is referred to as furunculosis or carbunculosis, respectively.
  • Cystic acne: This type of abscess is formed when oil ducts become clogged and infected. Cystic acne affects deeper skin tissue than the more superficial inflammation from common acne. Cystic acne is most common on the face and typically occurs in the teenage years.
  • Hidradenitis suppurativa: This is a condition in which multiple abscesses from under the armpits and often in the groin area. These areas are a result of local inflammation of the sweat glands. This form of skin infection is difficult to treat with antibiotics alone and typically requires a surgical procedure to remove the involved sweat glands to stop the skin inflammation.
  • Pilonidal cyst: This is a unique kind of abscess that occurs in the crease of the buttocks. Pilonidal cysts often begin as tiny areas of infection in the ski area’s base from which hair grows (the hair follicle). With irritation from direct pressure, over time, the inflamed area enlarges to become a firm, painful, and tender nodule that makes it difficult to sit without discomfort. These abscesses frequently form after long trips that involve prolonged sitting.

Boil vs. pimple

A pimple is a type of skin condition that can appear similar to a boil. Pimples are most commonly seen in people with acne of the face, back, or chest. Pimples may, at times, be filled with pus (like a boil) in addition to dead skin cells and oily secretions. Like boils, pimples start in pores that are openings for hair follicles in the skin. A boil is typically reddened and causes more pain than a pimple. Some pimples and boils may be indistinguishable. These two conditions arise from a similar inflammatory process occurring in the hair follicles, with boils being more severe and representing actual infections.

The bacteria present inside the boil can be contagious to others, especially if there is direct skin-to-skin contact with the secretions from an open boil.

Risk Factors of Boils

Anyone can develop a boil. However, people with certain illnesses or who take certain medications that weaken the body’s immune system (the natural defense system against foreign materials or microbes) are more likely to develop boils. Diseases that are associated with impaired immune systems include diabetes and kidney failure. Conditions in which there is inadequate antibody production (such as hypogammaglobulinemia) can also increase the risk of developing boils.


Many medications can suppress the regular immune system and increase the risk of developing boils and other infections. These medications include cortisone medications and medications used for cancer chemotherapy.

Diagnosing Boils

The diagnosis of a boil can be made by observation of the typical signs and symptoms. Blood tests or specialized laboratory tests are not required to complete the diagnosis of a boil. If the infection within a boil has spread to deeper tissues or is extensive, cultures of the pus may be taken from the wound area to identify the precise type of bacteria responsible for the infection. This can guide the choice of antibiotics for treatment.


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While boils typically resolve on their own and have an excellent prognosis, there are special situations in which medical care should be sought when abscesses develop. Rarely, boils may spread or persist, leading to more widespread infections.

Any boil or abscess in a patient with diabetes or a patient with an underlying disease that can be associated with a weakened immune system (such as cancer, rheumatoid arthritis, etc.) should be evaluated by a health care professional. Additionally, many medicines, especially prednisone, that suppress the immune system (the natural infection-fighting system of the body) can complicate what would be an otherwise simple boil. Those who are taking such medications should consult their health care professional if they develop boils.

Any boil that is associated with a fever should receive medical attention. Increasing reddening of the nearby skin and or forming red streaks on the skin (signs that the infection may be spreading), the failure of a boil to “form ahead,” and the development of multiple abscesses are other symptoms that warrant a visit to a health care professional. Medical attention is also required for boils in an infant. Abscesses located on the face, spine, groin, or rectum may also require medical attention.

A “pilonidal cyst,” a boil that occurs between the buttocks, is a particular case. These almost always require medical treatment, including drainage and packing (putting gauze in the opened abscess to assure it continues to drain). Finally, any painful boil that is not rapidly improving should be seen by a health care professional.

Prognosis (outcome) for Boils

The majority of boils in healthy people resolve on their own with home care without forming a scar. The prognosis is also excellent for abscesses treated in the health care setting by opening or lancing. Antibiotics may or may not be required after a boil has been lanced by a health care professional. Complications of an abscess are rare and are more likely to occur in people with suppressed immune systems.