Common Rashes Found in the Armpits

The armpit, or axilla, is prone to certain types of rashes. That's because of the characteristics of the skin there.

Armpit skin tends to be thinner than skin in other locations. It also folds upon itself and is especially hairy. That means moisture can accumulate. 

This article will help you identify common armpit rashes, what causes them, and how to treat or prevent them.

Allergic Contact Dermatitis

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Allergic contact dermaitis in armpit
Allergic contact dermaitis in armpit. DermNet / CC BY-NC-ND

Allergic contact dermatitis is a reaction that occurs when an allergy-triggering substance (allergen) comes into contact with the skin. It's a delayed-type hypersensitivity reaction. That means it doesn't happen right away.

You can become hypersensitized to an array of substances that your immune system recognizes as foreign.

It can take weeks before your first reaction. But then, when you come in contact with the trigger again, the rash can show up much faster.

Your armpit can become sensitized to ingredients in deodorants, antiperspirants, or shaving creams.

The rash often affects the area the allergen touched. It may be red, raised, irregularly shaped, and include blisters or crusting.

Irritant Contact Dermatitis

Irritant contact dermatitis is similar to allergic contact dermatitis. But the reaction isn't an allergy. It's the direct effect of an irritant or toxin on the skin.

Irritant contact dermatitis can also be caused by deodorants, antiperspirants, soaps, or body washes. 

The rash may be red, rough, or scaly. In severe cases, it can cause blisters.

Recap

Allergic contact dermatitis and irritant contact dermatitis are both reactions to something that bothers your skin. The allergic form is a hypersensitivity reaction. The irritant form is a direct effect on the skin. In the armpits, both types are often triggered by personal hygiene products.

Intertrigo

This photo contains content that some people may find graphic or disturbing.

Intertrigo in the armpit
Intertrigo in the armpit. Raimo Suhonen / DermNet / CC BY-NC-ND

Intertrigo is a rash that strikes in moist areas of skin folds. It's common in the armpits, under the breasts, and in the folds of the groin and abdomen.

The rash is often set off by yeast, fungi, or bacteria that thrive in a damp environment. They trigger your immune system. The immune response leads to skin inflammation and rash.

Symptoms include:

  • A roughly symmetrical red or reddish-brown rash with small bumps
  • Itching, stinging, and burning
  • Cracks and bleeding if left untreated
  • A foul smell and pus-containing bumps if it's infected

You can prevent intertrigo by keeping the skin dry. Treatments alleviate inflammation and fight the infectious organisms that trigger symptoms.

Erythrasma

This photo contains content that some people may find graphic or disturbing.

Erythrasma in armpit
Erythrasma in armpit. DermNet / CC BY-NC-ND 

Erythrasma is a rash that develops after infection with the Corynebacterium minutissimum bacteria. It's common in the armpits, under the breasts, in groin folds, and between the toes.

The rash is reddish and/or tan. It can cause slight wrinkling. It looks coral-red under a black light.

Erythrasma often has no other symptoms. Sometimes it may be mildly itchy. This rash is most commonly treated with the antibiotic erythromycin.

Recap

Intertrigo and erythrasma both occur in skin folds and involve infectious agents. Intertrigo can be fairly uncomfortable. Erythrasma may have a mild itch.

Tinea Corporis

This photo contains content that some people may find graphic or disturbing.

Tinea corporis in armpit
Tinea corporis in armpit. DermNet / CC BY-NC-ND

Tinea corporis is commonly called “ringworm.” But it's a skin infection caused by a fungus, not a worm. Various fungal species can trigger it.

The name of the infection changes depending on where it is. In the underarm or behind the knee, it's tinea corporis. On the foot, it's tinea pedis (athlete's foot). In the groin, it's tinea cruris (jock itch).

The rash may be red and have raised borders. The borders may also have a thin layer of scale.

Its most distinctive quality is that it grows outward in a circle. Ringworm can be itchy and makes hair fall out.

This infection is most commonly treated with topical antifungal medications. Several kinds are available over the counter.

Acanthosis Nigricans

Acanthosis nigricans looks like dark, “velvety,” raised patches. It appears in skin folds of the armpits, groin, and around the neck. 

It may be linked to increased insulin in the blood from:

  • Obesity
  • Diabetes or insulin resistance
  • Hormonal changes
  • Certain medications
  • Cancer

In rare cases, it may cause a mild itch.

This condition isn't usually treated directly. Treating the underlying cause may help improve its appearance.

Recap

Tinea corporis (ringworm) is a fungal skin infection. It grows in expanding circles and may itch. It's treated with antifungal creams.

Acanthosis nigricans causes dark, velvety patches. It's a result of several underlying conditions. Treating those conditions can relieve the rash.

Summary

Many rashes can occur in the armpits. This is because the skin is thin and often moist.

Allergic contact dermatitis and irritant contact dermatitis are reactions to things like deodorant or soap. Intertrigo and erythrasma are caused by infectious agents.

Tinea corporis is a fungal skin infection that grows in rings (ringworm). Acanthosis nigricans is tied to several medical conditions. It causes dark, velvety patches of skin.

A Word From Verywell

Some rashes are itchy and uncomfortable. Others just look bad. Regardless, you should see a healthcare provider for diagnosis and treatment.

Left untreated, some rashes may spread or lead to skin infections. If you suspect a rash is infected, get quick treatment to keep it from getting worse.

Frequently Asked Questions

  • Why does my deodorant give me a rash?

    You're likely allergic to one or more fragrances or essential oils used in the deodorant. Propylene glycol, a preservative and moisturizer, can also cause a rash.

    Your allergist may be able to test you for allergies. But it can be hard to pinpoint the exact cause. Using a non-allergenic product might help.

  • What does it mean if my armpit is red and burning?

    Intertrigo is a common underarm rash. It causes burning and red maceration (when skin is soft and irritated from too much moisture).

    It can be caused by yeast or by friction between hot, moist folds of skin. It’s more common in people who are overweight or have diabetes.

  • Are dark patches of skin under my arms a sign of diabetes?

    Possibly. Acanthosis nigricans is a skin condition that causes patches of skin to darken and become velvet-like. It's common in the armpit. The condition is caused by too much insulin in your blood, so it’s a possible sign of diabetes.

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10 Sources
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