Abscess

How an abscess forms

When bacteria enter tissue, usually through a hair follicle, cut, insect bite or blocked gland, white blood cells rush in to fight them. Dead cells, bacteria and tissue fluid form pus. The body builds a wall of inflamed tissue around it to contain the infection. This wall is why abscesses feel firm and tender at first, then soft and fluctuant (fluid-filled) as pus collects, and why antibiotics struggle to reach the center.

Types of abscess

Skin abscess

A pyogenic skin abscess is a red, hot, painful swelling, often with a yellow-white head. A boil (furuncle) is an abscess around a hair follicle; a carbuncle is several joined together. See boils. Common sites are the armpits, groin, buttocks, thighs and back of the neck.

Dental abscess

Infection at the root of a tooth or in the gum causes throbbing toothache, tenderness to biting, a bad taste and facial swelling. See dental abscess.

Throat (pharyngeal) abscesses

• Peritonsillar abscess (quinsy): a complication of tonsillitis in teens and adults, with severe one-sided throat pain, a muffled voice, drooling and difficulty opening the mouth.
• Retropharyngeal abscess: behind the throat, mostly in young children, with fever, neck stiffness and difficulty swallowing.
• Parapharyngeal abscess: at the side of the neck.

These develop over days from a throat or tooth infection that spreads into the deep spaces of the neck. As the abscess grows, it can push the throat wall inward and narrow the airway. Noisy breathing, drooling and inability to lie flat are signs this is happening.

Nasal abscess

An abscess can form inside the nostril from an infected hair follicle (nasal furuncle), often after picking or plucking hairs, or in the nasal septum after an injury that causes a blood clot (septal hematoma) to become infected. The area between the upper lip and the bridge of the nose drains into veins near the brain, so a nose abscess with fever, eye swelling or headache needs urgent care. See abscess of the nose. Most nasal abscesses recover in 1 to 2 weeks after drainage and antibiotics.

Perianal abscess

A painful, swollen lump near the anus, from an infected anal gland. It needs drainage and can lead to a fistula. See perianal abscess.

Internal abscesses

Abscesses can form in the liver, lung, brain, kidney, spine, pelvis or abdomen, often after surgery, appendicitis, diverticulitis or spread through the blood. They cause fever, night sweats, weight loss and pain at the site, and are found with CT or ultrasound.

Causes and risk factors

• Staphylococcus aureus, including MRSA, causes most skin abscesses. See MRSA.
• Streptococci and mouth bacteria cause dental and throat abscesses.
• Gut bacteria cause abdominal and perianal abscesses.

Risk is higher with diabetes, a weakened immune system, IV drug use, obesity, poor hygiene, close-contact sports, crowded living, shaving and skin conditions such as hidradenitis suppurativa.

Diagnosis

Skin abscesses are usually diagnosed by examination. A bedside ultrasound can confirm pus under the skin. Pus may be swabbed to identify the bacteria and guide antibiotics, especially for recurrent infections. Throat and internal abscesses need CT or MRI. Blood tests check for spreading infection.

Treatment

Incision and drainage

Most abscesses larger than about 1 cm need draining. Under local anesthetic, the doctor makes a small cut, lets the pus out, washes the cavity and may pack it with gauze. Pain usually improves quickly afterward.

Internal abscesses are drained with a needle or tube guided by CT or ultrasound, or surgically. Throat abscesses are drained through the mouth or neck, sometimes in the operating room with airway protection.

Antibiotics

Antibiotics are added when the abscess is large, has surrounding cellulitis, is on the face or hand, or the person has fever, diabetes or a weak immune system. They are also needed for dental, throat and internal abscesses.

Home care for small skin abscesses

• Apply warm, moist compresses for 10 to 15 minutes, 3 to 4 times a day, to help it come to a head and drain.
• Do not squeeze or cut it yourself, which can push infection deeper.
• After drainage, keep the wound covered, change dressings as instructed and wash hands well.
• Use acetaminophen (paracetamol) or ibuprofen for pain, following the label dose.

Complications

• spreading skin infection (cellulitis)
• sepsis
• fistula formation (perianal)
• airway obstruction (throat abscesses)
• spread to bone, joints, heart valves or brain (rare)
• recurrence, especially with MRSA

Preventing recurrent abscesses

Keep cuts clean and covered, do not share razors or towels, wash hands often, and manage diabetes. For repeated MRSA abscesses, a doctor may recommend a decolonization routine with antiseptic body washes and nasal ointment for the whole household.

Frequently asked questions

What is a pyogenic abscess of the skin?

It is a pus-filled skin infection, usually caused by Staphylococcus aureus. It appears as a painful, red, warm lump that softens as pus collects, sometimes with a white or yellow center. Most need draining by a clinician, and some need antibiotics.

What does it mean if an abscess is narrowing the pharyngeal airway?

It means a throat abscess has grown large enough to push the throat wall inward and reduce space for air. This causes noisy breathing, drooling and difficulty swallowing and is a medical emergency needing airway protection and urgent drainage.

How does a throat abscess develop?

A throat abscess usually starts as tonsillitis, a throat infection or a dental infection. Bacteria spread into the tissue spaces beside or behind the throat, where pus collects over several days. Fever, worsening one-sided pain and difficulty opening the mouth are typical signs.

Will an abscess go away on its own?

Very small boils may drain and heal with warm compresses. Larger abscesses usually do not resolve on their own and need drainage, because the pus is walled off and antibiotics alone cannot clear it well. Leaving them can lead to spreading infection.

How long does it take an abscess to heal after drainage?

Pain usually eases within a day or two. A drained skin abscess generally heals over 1 to 2 weeks, depending on its size. Deeper or internal abscesses can take longer and may need several weeks of antibiotics.