Armpit Boil: Causes, Treatment, and When to Seek Care

By Your Health Magazine Health Information Team

An armpit boil is a painful, pus-filled infection that usually begins in a hair follicle. Small boils may improve with warm compresses and careful wound care, but you should not squeeze, pierce, or cut one open. A large, worsening, repeatedly returning, or fever-associated boil may require medical drainage, antibiotics, or evaluation for another condition such as hidradenitis suppurativa.

What Does an Armpit Boil Look and Feel Like?

A boil, also called a furuncle, commonly starts as a firm, tender bump. It may become larger, warmer, red or discolored, and increasingly painful as pus collects beneath the skin. A white or yellow center may develop, and the boil may eventually drain.

Redness can be less noticeable on brown or black skin, so warmth, swelling, tenderness, drainage, and changes from your usual skin color may be more useful signs. Several connected boils can form a larger infected area called a carbuncle.

A lump in the armpit is not always a boil. Other possibilities include an irritated or ingrown hair, inflamed cyst, swollen lymph node, contact reaction, or hidradenitis suppurativa. A clinician can examine a lump when its cause is unclear.

What Causes a Boil in the Armpit?

Most boils develop when bacteria—often Staphylococcus aureus, or staph—infect a hair follicle or enter through damaged skin. The armpit is particularly vulnerable because it contains hair follicles and is exposed to moisture, friction, shaving, and skin-to-skin contact.

Factors that may contribute to an armpit boil include:

Small cuts or irritation from shaving
Friction from clothing, sports equipment, or repeated arm movement
Excessive sweating and prolonged moisture
Sharing razors, towels, or other personal items
Close contact with someone who has a draining skin infection
Skin conditions that damage the protective skin barrier
Diabetes, immune suppression, or certain other health conditions

Some boils are caused by methicillin-resistant Staphylococcus aureus (MRSA). A MRSA infection cannot be identified by appearance alone; laboratory testing of drainage may be needed. The CDC provides additional information about MRSA skin infection symptoms and diagnosis.

How to Treat a Small Armpit Boil at Home

Home care may be reasonable for a small boil when you do not have fever, spreading redness, severe pain, or a condition that weakens your immune system.

Apply a warm compress. Hold a clean, warm, moist cloth against the area for about 10 minutes several times a day. Use comfortably warm—not scalding—water. Moist heat may ease discomfort and encourage natural drainage.
Do not pop or puncture it. Squeezing can push infection deeper, spread bacteria to nearby skin, and increase scarring.
Keep the area clean. Wash gently with soap and water. Avoid vigorous scrubbing and stop shaving over the affected skin until it heals.
Cover drainage. If the boil opens, place clean, dry gauze or a bandage over it. Change the covering when it becomes wet or dirty, and wash your hands before and after wound care.
Avoid sharing personal items. Do not share razors, towels, washcloths, deodorant applicators, or clothing that has touched the area.

For pain, an over-the-counter pain reliever may help if it is normally safe for you. Follow the product label and ask a pharmacist or healthcare professional if you have kidney disease, liver disease, a history of stomach bleeding, take blood thinners, are pregnant, or are unsure which option is appropriate.

Do not automatically apply leftover antibiotic creams. An established pocket of pus may require drainage, and the appropriate treatment depends on the cause. Learn more about using mupirocin on sensitive skin areas, and use prescription antibiotics only as directed by a healthcare professional.

Medical Treatment for an Armpit Boil

Situation	Possible medical approach
Large, deep, or very painful abscess	A clinician may numb the area and make a small opening to drain the pus.
Spreading redness, fever, or significant infection risk	Oral antibiotics may be prescribed in addition to drainage when clinically appropriate.
Unusual or recurring infection	Drainage may be cultured to identify the bacteria and determine which antibiotics are likely to work.
Repeated boil-like lumps in the armpits	Evaluation for hidradenitis suppurativa or another underlying condition may be recommended.

Drainage is often an important part of treating a true skin abscess. Antibiotics are not necessary for every uncomplicated boil, and they should not be started, stopped, or changed without professional guidance. For additional reliable consumer information about skin infections and related conditions, explore MedlinePlus health topics.

Could Repeated Armpit Boils Be Hidradenitis Suppurativa?

Boil-like lumps that repeatedly appear in one or both armpits may be a sign of hidradenitis suppurativa, or HS. This chronic inflammatory skin condition commonly affects areas where skin rubs together, including the armpits, groin, buttocks, and beneath the breasts.

Features that make HS more likely include:

Deep, painful lumps that return in the same areas
More than one lump at a time
Drainage containing pus or blood
Blackhead-like spots near the affected area
Scarring or firm bands beneath the skin
Tunnels connecting recurrent sores under the skin

HS is not contagious and is not simply caused by poor hygiene. Early diagnosis can help control symptoms and reduce additional scarring. The American Academy of Dermatology explains the typical signs and symptoms of hidradenitis suppurativa.

When to Seek Care

Contact a primary care clinician, dermatologist, or urgent care clinic if the armpit boil is large, very painful, rapidly growing, not improving after several days of home care, or has not healed within about one to two weeks. Evaluation is also appropriate if boils keep returning or multiple household members develop similar infections.

Seek prompt medical care if you have:

Fever, chills, weakness, or a general feeling of illness
Redness, swelling, warmth, or pain spreading away from the boil
Red streaks extending from the affected area
Rapidly worsening pain or swelling
Difficulty moving your arm because of pain or swelling
Diabetes, immune suppression, or another condition that increases infection risk

Until the area heals, keep it clean and covered, avoid picking at it, wash your hands after touching the dressing, and do not share towels or razors. These measures can reduce the chance of spreading bacteria to other skin areas or other people.