What Is an Abscess?

Understanding the Causes and Ways to Prevent Them

An illustration of a boil forming under the skin.
An illustration of a boil forming under the skin. Dorling Kindersley/Getty Images

A skin abscess is a walled-off, bump-like collection of pus that appears either within or just below the surface of the skin. Abscesses are typically caused by a bacterial infection and tend to appear on the back, chest, buttocks, and certain areas of the face. Sometimes they develop in areas where hair is present, such as the armpits and pubic area.

A furuncle — sometimes called a boil — is caused when a hair follicle becomes infected and creates a small abscess.

A carbuncle is defined as multiple pus-draining follicles that combine to create a single infected mass.

Furuncles and carbuncles tend to appear in areas of hairy skin that been exposed to minor trauma, sweat, or friction (such as beneath the belt or where the skin has been irritated from shaving). 

Causes of Abscesses

Abscesses are most often caused by a bacteria, called Staphylococcus aureus, which normally exists on the skin and inside the nose. It can enter the body through a cut, abrasion, puncture, or even an insect bite.

Other factors can increase the risk of S. aureus infection, including:

  • a chronic skin condition such as acne or eczema
  • diabetes
  • a weakened immune system
  • coming into close contact with an infected person
  • poor hygiene

Another condition called folliculitis can cause an abscess to form within a hair follicle. Infection begins when a hair is trapped beneath the surface and can't break through (a condition commonly referred to as an ingrown hair).

Folliculitis can be caused by shaving (particularly in black men) and is also associated with swimming in an improperly chlorinated pool or hot tub.

Symptoms of Abscesses

An abscess looks like a little bump or pimple that can grow into an inflamed, fluid-filled cyst. The skin surrounding an abscess is often painful and warm to the touch.

In some cases, an abscess can be extremely hard and firm (indurated).

Depending on the cause, the appearance of an abscess may be accompanied by fever, nausea, or swollen lymph nodes (lymphadenopathy).

Diagnosis is usually made on appearance alone. While smaller abscesses can usually be treated at home, medical attention should be considered if any of the following occurs:

  • development of an abscess on the face
  • development of multiple abscesses
  • worsening or extremely painful abscesses
  • abscesses of more than two inches in diameter
  • abscesses that persist for more than two weeks
  • abscesses that recur

Treatment of Abscesses

Small abscesses can be treated at home with a warm compress to relieve pain and promote drainage. A larger abscess may need be drained at the doctor's office to both relieve the pain and treat the infection.

Depending on the cause of an abscess, a doctor may consider whether or not an antibiotic is needed. Typically speaking, abscesses of less than two centimeters in a healthy individual generally do not require an antibiotic.

On the other hand, antibiotics are customarily prescribed to persons who have a weakened immune system or are experiencing whole-body symptoms like fever.

In such cases, a doctor may take a pus sample to better evaluate the cause and ensure that the bacteria is not drug resistant.

It is important that you not drain an abscess at home as this can worsen the infection. Always wash your hands after touching an abscess and clean anything comes in contact with it, including clothing and compresses.

Prevention of Abscesses

While abscesses are not entirely avoidable, there are a few simple measures you can take to better prevent them:

  • Always wash your hands, ideally with an antibacterial cleanser.
  • Treat any cuts with care, keeping them clean, covered, and dry until they are fully healed.
  • Do not share personal items like razors, towels, lipstick, or lip balm.
  • Avoid cutting yourself when shaving your underarms or pubic area.

Source:

Wolf, K; Johnson, R.; and Suurman, R.. "Section 22. Bacterial infections involving the skin." Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology (5th ed.). 2005; McGraw-Hill Professional; ISBN-13 978-0071440196.

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