Itchy bumps or oozing blisters? Here's what might be going on.

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A rash in your armpit, or "axilla," as doctors call it, can be mild or severe; short-lived or chronic, and treatments may depend on the underlying cause (over-the-counter creams can work best for some rashes, while others require a doctor's script).

Any time you have lingering symptoms—like an itchy, irritated armpit—it's not a bad idea to see a physician who specializes in skin conditions. Keep reading to get the lowdown on armpit rashes and what to do about them.

Reasons You Have an Armpit Rash—And How to Treat It
Credit: Getty Images

Contact dermatitis

This rash is caused by an exposure to something that irritates the skin or causes an allergic reaction, according to the Mayo Clinic.

Contact dermatitis is probably the most common cause of armpit rashes, Lisa Chipps, MD, a Los Angeles-based board-certified dermatologist, tells Health. Patients usually come in with a story, "like they're worried about the deodorant that they just applied the last few months or weeks."

There are two main types of contact dermatitis, and per Mayo Clinic and the American Academy of Dermatology (AAD), each can cause an itchy, burning, or painful rash.

  • Allergic contact dermatitis, which occurs when skin comes in contact with a substance that provokes an immune response. Your rash could be an allergic reaction to fragrances and preservatives in soap and skin products, for example, or poison ivy (presuming you recently had a brush with this poisonous plant).
  • Irritant contact dermatitis, the more common type of contact dermatitis, says Cleveland Clinic. It's caused by repeated exposure to an irritant. Such exposures may include applied products such as deodorants, antiperspirants, soaps, or washes.

It's possible to have both types of contact dermatitis, Yale Medicine points out.

So what's the solution? The best advice is to avoid the allergen or irritant. "Usually when you discontinue the offending product, usually you can clear up the rash," says Dr. Chipps. "And sometimes we'll prescribe some anti-inflammatory creams to use to get the patient to feel better faster," she adds. In more severe cases, Yale Medicine says doctors may recommend oral steroids, such as prednisone, to relieve an itchy rash.

Hidradenitis suppurativa (HS)

Also known as acne inversa, HS is a chronic inflammatory skin condition. It begins as a blockage of hair follicles in areas of the body where certain sweat glands (called apocrine sweat glands) reside, says the US National Library of Medicine (NLM).

"One of the major areas that it occurs is in the axilla, but it could certainly occur in the groin," Amy McMichael, MD, professor and chair of the Department of Dermatology at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, tells Health.

While anyone can develop this condition, it's more common in women, particularly African Americans females, per the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).

In its mildest form, HS produces small, painful, pus-filled bumps. They may look reddish, purplish, or darker brown, depending on a person's skin color, says Dr. McMichael. As HS progresses, larger nodules can develop. The bumps can rupture and leak foul-smelling fluid and pus, says the NLM. Tracks or tunnels connecting the wounds may form beneath the surface of the skin, leading to scarring and even keloids, notes Dr. McMichael.

Treatment, she says, depends on the severity of the disease. Topically applied cleansers and antibiotics might be the first choice for mild disease. For moderate disease, options include various oral medications and combination therapies. Adalimumab (Humira), an injectable biologic, is approved for moderate-to-severe disease, says the AAD. Various surgical procedures may be performed to allow the pus-filled lesions to drain and heal.

Folliculitis

A zit-like rash in your armpits? Maybe it's folliculitis, a common condition that occurs when hair follicles become swollen or infected, per the Cleveland Clinic.  

"We see that most often when people are shaving too close to the skin and then getting ingrown hairs or little nicks in the skin that allow the normal skin bacteria to penetrate and get in under the skin," says Dr. Chipps.

Treatment may depend on type and severity of the rash, Fred H. Brennan, Jr., DO, assistant director of the University of South Florida-BayCare family medicine and sports medicine programs in Clearwater, Florida, tells Health. For a mild, pimply rash, it may be best to stop shaving for a couple of days and apply an over-the-counter topical steroid, like hydrocortisone cream a couple times a day, he says. For a more severe rash, where the bumps are topped by pustules, or little whiteheads, you may need an antibiotic. "That means you have a pretty good infection brewing there," he says.

Laser hair removal can be helpful to reduce the thickness of the hair and decrease hair growth in the area, notes Dr. McMichael.

Acanthosis nigricans (AN)

AN is not a rash, per se. It's a velvety thickening of the skin in the body's folds and creases, and that includes the armpits, per the Mayo Clinic. These patches appear darker in color than the surrounding skin.

Acanthosis nigricans has been linked to insulin resistance (due to diabetes or pre-diabetes, for example), hormonal irregularities (like thyroid disease), and use of certain drugs (such as birth control pills or steroids), notes the Cleveland Clinic. People who are overweight, have a family history of AN, or have darker skin are at greater risk of developing this skin condition, it says. Although AN usually develops slowly, its sudden appearance may be a sign of cancer, the Cleveland Clinic cautions.

If there's an underlying medical cause, addressing the issue may help—managing insulin resistance, for example. To reduce the appearance of AN, dermatologists may suggest various topical agents (such as retinoids), oral retinoids (isotretinoin, for one), or chemical peels.

Dr. McMichael sees patients who've tried to lighten the patches under their pits with bleaching cream, something she does not recommend for the sensitive skin of the axilla. "When you try to treat it with a bleaching agent, it just doesn't work, and it can be very irritating."

Intertrigo

Chafing, or skin rubbing against skin, especially in warm or moist areas of the body, can cause this itchy or burning rash known as intertrigo, says the American Academy of Family Physicians (AAFP).

It can appear red-to-violet in color or even just hyperpigmented, says Dr. McMichael. "We typically see it most commonly under the breast, but you could get it in the underarms too," she says.

Intertrigo affects the outer layers of skin, says the NLM. These so-called intertriginous areas can ooze, crack, or bleed, says AAFP, and as the skin breaks down, it becomes vulnerable to infection.

Keeping skin folds cool and dry can help with healing and prevent recurrences, says AAFP. As for treatment, NLM says options include antibiotic or antifungal creams, topical steroid cream, and drying agents (such as antiperspirant or absorbent powder).

Inverse psoriasis

This is a type of rash that affects the body's skin folds, says the National Psoriasis Foundation. One study published in the journal Clinical and Experimental Dermatology found that it affects 24% to 30% of people with psoriasis. Unlike the white, scaly patches that psoriasis usually produces, inverse psoriasis (aka intertriginous psoriasis) can be smooth and shiny, the foundation notes. And it can be sore and itchy.

"A lot of times people think they have intertrigo or yeast," says Dr. McMichael. But the key to treatment is getting a proper diagnosis: "You could put all the anti-yeast medicine you want on that, and if you don't biopsy it and find out that it's psoriasis, then you'll miss the boat," she says.

Topical steroids are usually the first choice of treatment, per the foundation, although more severe cases may require oral medication or biologic therapy.

Ringworm

Ringworm is an itchy, scaly rash that forms a ring-like pattern on the skin. It belongs to group of diseases called tinea, which are caused by fungi, per the NLM.

"Just like people get athlete's foot or jock itch, sometimes they can get a fungal infection in the armpit from moisture and heat," explains Dr. Chipps.

Ringworm spreads via contact with an infected person or animal or by touching a surface where the fungi like to live, says the CDC. While anyone can get ringworm, athletes are more vulnerable, particularly those involved in contact sports. Wrestlers might get it under their arms from skin-to-skin contact, for example. You can also get ringworm by sharing towels or other personal items with someone who has the infection, the CDC explains.

Ringworm is typically treated topically with an over-the-counter or prescription antifungal medication, the CDC notes.

Cutaneous candidiasis (yeast)

Yeast thrives in warm, moist creases of the body, per the NLM, and that includes your armpits. Candidiasis is simply a yeast infection of the skin.

The same fungus that causes most vaginal yeast infections, Candida albicans, is often responsible for skin infections too, says NLM. These infections are the result of an overgrowth of yeast normally found on your skin, says Johns Hopkins Medicine. Sometimes they're a complication of intertrigo, says NLM.

This type of rash may be pimply and can itch, burn, or ooze, per Johns Hopkins. The go-to treatment? Antifungal powders.

Heat rash (prickly heat)

Yes, you can get a pimply underarm rash from being overheated. But unlike a fungal infection, which can take some time to clear up, a heat rash is fleeting.

"It's more of an inflammatory process that goes away when you cool the skin," says Dr. Chipps. "It doesn't linger around."

This type of rash (also called miliaria) occurs when sweat glands and ducts become obstructed by bacteria, skin cells, oil, or other debris. Clusters of pimples or small blisters make your skin feel itchy or irritated—causing prickly, tingling pain, according to the AAFP.

If you keep your skin cool and dry, the rash should clear up on its own, says Johns Hopkins Medicine. Sometimes doctors prescribe a corticosteroid lotion.

Cutaneous lymphoma (skin lymphoma)

Cutaneous lymphoma, or lymphoma of the skin, is an uncommon type of cancer, says the American Cancer Society (ACS). It begins in white blood cells called lymphocytes, which are part of the body's immune system.

Skin lymphomas may appear as pimples, flat patches, thick plaques, or nodules, says ACS. They may be itchy and range in color from red to purple. If the cancer reaches the lymph nodes, you may feel a lump in your armpit area.

Most skin lymphomas have no known cause. Having a weakened immune system can boost your risk of developing skin lymphoma, although it's not clear why, says ACS.

Various treatments may be recommended depending on the type, location, and stage of the cancer.

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