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The arrangement of the chest wall, shoulder bones and muscles, and the upper arm create a small hollow called the armpit. The armpit is the underside of the shoulder joint, and is among the warmest areas of the body. The armpit is also called the axilla.
Blood and lymph vessels serving the arm travel through the armpit. There are more than 20 lymph nodes (small lumps of tissue that are part of the body's lymphatic system, which helps fight infection) in the armpit. These lymph nodes normally cannot be felt through the skin. The armpits have a high concentration of hair follicles and sweat glands.
- Hyperhidrosis: Excessive sweating, which often affects the armpits and hands. The cause is unknown; the perspiration is not due to anxiety or stress.
- Irritant contact dermatitis: Skin inflammation (redness, swelling, pain, or heat) caused by an irritating substance touching the skin. Soaps, deodorant, alcohol, and dry air may all cause irritant contact dermatitis of the armpit.
- Allergic contact dermatitis: An allergic reaction to something directly touching the skin, usually causing redness and small blisters. Irritant contact dermatitis affects the armpit more often than allergic contact dermatitis.
- Psoriasis: The armpits are often affected by psoriasis, a condition causing red plaques with a silvery scale to appear on the skin. Psoriasis is an autoimmune condition, meaning it is caused when the immune system mistakenly attacks the body's own tissues.
- Acanthosis nigricans: A skin disorder causing velvety, light brown to black markings on the skin of the armpits, neck, groin, and/or under the breasts.
- Tinea corporis (ringworm): A fungal infection of the uppermost layer of the skin (epidermis). Ringworm often creates a ring-shaped rash, although no worm is involved.
- Tinea axillaris: A term occasionally used for ringworm affecting the armpit.
- Candidiasis (yeast infection): A skin infection by the yeast Candida, causing irritated skin with white plaques. Candida grows best on warm, moist skin, and may affect the armpits.
- Intertrigo: A condition in which moist, warm skin becomes irritated and often mildly infected. Redness, itching, and burning of the skin in the armpits are common symptoms of intertrigo.
- Armpit abscess: When infected fluid (pus) collects in the armpit. The bacteria Staphylococcus is the most common cause.
- Hidradenitis suppurativa: A long-term (chronic) condition causing red, tender bumps in the skin of the armpits and/or groin. The bumps often turn into abscesses and can cause scarring over time.
- Erythrasma: A long-term (chronic) skin infection caused by the bacteria Corynebacterium. The infection causes red-brown, irritated patches of skin in the armpits or other moist areas of skin.
- Armpit boil (furuncle): A skin infection of a single hair follicle and surrounding skin. It causes a painful, red lump on the skin, which may grow into an abscess.
- Armpit folliculitis: Inflammation of the hair follicles, usually caused by bacterial infection. Most folliculitis is mild and goes away without specific treatment.
- Axillary lymphadenopathy: Enlargement of the lymph nodes of one or both armpits. The swelling may be caused by infection, cancer, or other causes and may be detected during a doctor’s examination or on imaging tests.
- Armpit skin tags (acrochordons): Harmless, small flaps of skin that commonly occur on the neck or armpits. Skin tags are more common with older age.
- Physical examination: By observing and palpating (feeling) the armpit, a doctor may find enlarged lymph nodes or other armpit conditions.
- Axillary lymph node biopsy: Part or all of a lymph node is removed from the armpit and examined under a microscope, sometimes to look for cancer.
- Ultrasound: A device placed on the surface of the skin bounces high-frequency sound waves off the structures in the armpit. The signals are converted into images on a video screen, allowing health care providers to see structures inside the body.
- Computed tomography (CT scan): A CT scanner takes multiple X-rays, and a computer compiles the X-rays into images of the armpit and nearby structures.
- Magnetic resonance imaging (MRI scan): An MRI scanner uses a high-powered magnet and a computer to create detailed images of the armpit and adjacent body areas.
- Skin moisturizers: Because skin dryness makes many skin conditions worse, moisturizing the skin can be helpful in many armpit conditions.
- Topical steroids: Creams or ointments that contain cortisone, which reduces skin inflammation. Topical steroids can reduce skin itching and irritation in the armpit.
- Axillary lymph node dissection: Removal of one or all of the armpit’s lymph nodes. This is often done as part of the surgical treatment for breast cancer. Examining the removed lymph node(s) helps identify whether and how much the breast cancer has spread.
- Antiperspirant: Special prescription-strength antiperspirants can help control the excessive armpit sweating of hyperhidrosis.
- Botulinum toxin injection (Botox): A doctor may inject Botox into the sweat glands of the armpit; this can reduce the excessive sweating of hyperhidrosis.
- Incision and drainage: Armpit abscesses often must be cut open and drained by a health care provider in order to allow proper healing.
- Antibiotics: Skin infections in the armpit caused by bacteria can usually be treated with antibiotics.
- Endoscopic thoracic sympathectomy: A surgical treatment for hyperhidrosis, in which nerves that contribute to sweating are cut. In successful cases, excessive sweating is noticeably improved.
- Topical antifungals: Fungal infections of the armpit (such as with Candida) can usually be treated with topical creams and ointments containing antifungal drugs.
- Skin tag removal: Doctors can remove skin tags using scissors or scalpel, electric cautery (burning), tying them off with string, or freezing them with liquid nitrogen.