Abscess

A skin abscess is a localized collection of pus that generally develops in response to infection or to the presence of other foreign materials under the skin. An abscess is typically painful, and it appears as a swollen area that is warm to the touch. The skin surrounding an abscess often appears pink or red.

Abscesses can develop in many parts of the body, but they usually involve the skin surface. Skin abscesses are also referred to as boils, especially when they affect the deeper, or subcutaneous, layers of the skin. Common sites affected by abscesses include the armpits (axillary area) and inner thigh (groin), called hidradenitis suppurativa, also known as acne inversa (AI). Other types of abscesses involve the rectal area (perirectal abscess), the external vaginal area (Bartholin's abscess), and along the tailbone (pilonidal abscess). Inflammation surrounding hair follicles or sweat glands can also lead to the formation of abscesses. Abscesses can affect any organ, including the brain, kidneys, liver (hepatic abscess), stomach or intra-abdominal area, lungs, breast, neck, face, cheeks, multiple teeth or an individual tooth (dental abscess), gums, throat, or tonsils (peritonsillar abscess). Abscesses can also occur anywhere on the body, such as the fingers and toes, eyes, shoulders, knees, or a foot/both feet.

An abscess is not the same thing as a cyst. Both are fluid-filled lumps, but an abscess is infected while a cyst is not. However, a cyst can become infected and turn into an abscess.

Unlike other infections, antibiotics alone will not typically cure a skin abscess. In general, abscesses must open and drain to improve. Although sometimes an abscess will open and drain spontaneously, it often needs to be lanced (incision and drainage) by a health care provider. Certain abscesses may require a surgical drainage procedure in an operating room.

Picture of drainage of a skin abscess

Skin abscesses are typically caused by either an inflammatory reaction to an infectious process (bacteria or parasite) or, less commonly, to a foreign substance within the body (a needle or a splinter, for example). Abscesses may develop because of obstructed oil (sebaceous) or sweat glands, inflammation of hair follicles on the body or scalp, or from minor breaks and punctures of the skin. Abscesses may also develop after a surgical procedure.

The infectious organisms or foreign material cause an inflammatory response in the body, which triggers the body's immune system to form a cavity or capsule to contain the infection and prevent it from spreading to other parts of the body. The interior of the abscess liquefies, and pus develops (which contains dead cells, proteins, bacteria, and other debris). This area then begins to expand, creating increasing tension and inflammation of the overlying skin.

The most common bacterial organism responsible for the development of skin abscesses is Staphylococcus aureus, although various other organisms can also lead to abscess formation. With the emergence of methicillin-resistant Staphylococcus aureus (MRSA), health care providers must now consider this organism as the possible cause when a skin abscess is encountered.

A major risk factor for developing skin abscesses includes a weakened immune system (either from chronic diseases or from medications), because the body's ability to fight infection is decreased. The following conditions are risk factors for developing abscesses and for getting recurrent or multiple abscesses:

• Chronic steroid therapy
• Chemotherapy
• Diabetes
• Cancer
• Lupus
• Dialysis for kidney failure
• HIV/AIDS
• Sickle cell disease
• Peripheral vascular disease
• Crohn's disease
• Ulcerative colitis
• Severe burns
• Severe trauma
• Intravenous (IV) drug use
• Skin injections from medical procedures, prescription drugs, or tattoos
• Alcoholism

The symptoms of a skin abscess vary depending on the location of the abscess, but in general, individuals will experience the following:

• A painful, compressible mass that is red, warm to the touch, and tender.
• As an abscess progresses, it may "point" and come to a head. Pustular drainage and spontaneous rupture may occur.
• Most abscesses will continue to worsen without care and proper incision and drainage. The infection can potentially spread to deeper tissues and even into the bloodstream.
• If the infection spreads, fever, nausea, vomiting, increasing pain, and increasing skin redness may develop.

A skin abscess will sometimes rupture and drain spontaneously at home without any further complications. A ruptured abscess can be a good thing because the pus is released and the body has a better chance to heal on its own. However, in some instances, further evaluation by a doctor is necessary to prevent the progression and complications associated with a continuing infection. Consult a doctor if any of the following scenarios occurs with an abscess:

• The sore is larger than 1 cm or ½ inch across.
• The sore fails to heal or it continues to enlarge and becomes more painful.
• The person has an underlying illness such as HIV/AIDS, cancer, diabetes, sickle cell disease, or peripheral vascular disease.
• The person is an IV drug abuser.
• The person is on steroid therapy, chemotherapy, other drugs that suppress the immune system, or dialysis.
• The sore is located at the top of the buttock crease, or it is on or near the rectal or groin area.
• The person has a fever of 100.4 F (38 C) or higher.
• There is a concern that there is foreign material within a wound or under the skin.
• The person is pregnant.
• The abscess gets better but then returns.

Go to a hospital's emergency department if any of these conditions occur with an abscess:

• Fever of 102 F (38.9 C) or higher, or vomiting, especially if the person has a chronic disease or is on steroids, chemotherapy or other immunosuppressive medications, or dialysis
• There is a spreading red streak on the skin originating from the abscess.
• Any facial abscess larger than 1 cm or ½ inch across

A skin abscess may be treated by a primary care provider (PCP), such as a general practitioner, family medicine specialist, internist, or pediatrician. One may also be seen by an emergency medicine specialist in a hospital emergency department. If surgery is required, a general surgeon can treat an abscess. A dermatologist, who specializes in disorders of the skin, may also treat a skin abscess.

The doctor will take a medical history and ask for information about the following:

• How long the abscess has been present
• If the patient recalls any injury to that area
• What medicines the patient is taking and if there are any serious or chronic medical conditions
• If the patient has any allergies
• If the patient had a fever at home
• The doctor will examine the abscess and surrounding areas. If it is near the anus or vagina, the doctor will perform a rectal or vaginal exam. If an arm or leg is involved, the doctor will feel for an enlarged lymph node either in the groin or under the arm.
• Depending on the location and the extent of the abscess, the doctor may obtain wound cultures or blood tests and imaging studies, although these tests are often not needed.

• If the abscess is small (less than 1 cm or less than ½ inch across), applying warm compresses to the area for about 30 minutes, four times daily may help.
• Once the boil drains, it should heal on its own, though this may take several weeks.
• Do not attempt to drain the abscess by pressing on it. This can push the infected material into the deeper tissues.
• Do not stick a needle or other sharp instrument into the abscess because it may injure an underlying blood vessel or cause the infection to spread.

Often, a skin abscess will not heal on its own without further intervention by a health care provider. Initially, an abscess may feel firm and hardened (indurated), at which time incision and drainage may not be possible. However, once the abscess begins to "come to a head" and it becomes softer and fluid-filled, a minor surgery to lance it to evacuate the pus and relieve the pressure is the best course of action. A doctor will open and drain the abscess (incision and drainage) using the following technique:

• The area around the abscess will be numbed with local anesthetic.
  • It is often difficult to completely numb the area, but in general, local anesthesia can make the procedure almost painless.
  • A sedative may be given if the abscess is large.
• The affected area will be covered with an antiseptic solution and sterile towels placed around it.
• The doctor will cut open the abscess with a scalpel and drain as much of the pus and debris as possible. Sometimes, there will be multiple pockets of pus that must be identified and drained.
• Once the sore has drained, the doctor may insert packing into the remaining cavity to minimize bleeding and to keep the wound open for a day or two so any remaining pus can continue to drain.
  • A bandage will then be placed over the packing, and the patient will be given instructions for home care.
  • Most people feel better immediately after the abscess is drained.
  • A doctor may prescribe pain medication, depending upon the location, size, and extent of the abscess.
  • Antibiotics are generally not necessary; however, they may be prescribed if the abscess is associated with a surrounding skin infection. Antibiotics such as trimethoprim/sulfamethoxazole (Bactrim), cephalexin (Keflex), or azithromycin (Zithromax Z-pak) may also be prescribed, depending upon the location of an abscess and whether or not the individual has a compromised immune system.

• Carefully follow any instructions regarding wound care recommended by a health care provider.
  • A health care provider may have the patient or the caregiver remove the packing. If so, removal works best while the area is moistened with water.
  • After the packing has been removed, soak or flush the area for 10-20 minutes, three to four times daily to allow the wound to heal properly.
• Keep all follow-up appointments as a health care provider may want one to return for a recheck of the wound. Sometimes the wound may require repacking if it continues to drain pus.
• Report any fever or increased pain or redness to a health care provider immediately.

• Maintain good personal hygiene by washing the skin with soap and water regularly.
• Take care to avoid cutting oneself when shaving the underarms or pubic area.
• Seek medical attention for any puncture wounds:
  • Especially if the person thinks there may be some foreign material or debris inside the wound or under the skin
  • If the person has one of the listed medical conditions that may weaken the immune system
  • If the person is on steroids, chemotherapy or other immunosuppressive medications, or dialysis

• Once treated, the skin abscess should heal. The prognosis is generally excellent, but some individuals may suffer from recurrent abscesses requiring medical attention.
• Most people do not require antibiotics.
• The pain should improve almost immediately after drainage and subside more each day.
• Soak or wash the area daily until the wound heals -- about seven to 10 days.
• Usually one can remove the packing by the second day. It rarely needs to be replaced.
• After the first two days, drainage from the abscess should be minimal to none. Healing of sores should occur in 10-14 days.