Common armpit rashes.


The armpit is more formally known as armpit ( armpit in plural). It is an area of the body prone to certain types of rashes due to certain characteristics of the skin.

The skin is usually thinner here than elsewhere, like on the back, and folds on its own. Therefore, it can be exposed to moisture. It is also the scalp. Here we provide an overview of the various rashes that can affect the armpits.

Allergic contact dermatitis.

Allergic contact dermatitis is a reaction to an external agent with which the skin comes in contact. This is a delayed-type hypersensitivity reaction , which means that the reaction does not occur immediately, but takes several days to develop.

Sensitization is the process by which the body's immune system recognizes an external agent as foreign. This can take several weeks. With repeated contact with the pathogen, the rash can appear after a much shorter period of time.

The agents used may include ingredients found in deodorants, antiperspirants, or shaving creams. The rash will often follow the area where the product has been applied, often creating "unnatural" shapes and geometric edges that hint at "outside work." The rash is usually red, raised, and may include blisters or scabs .

Allergic contact dermatitis of the armpit. DermNet / CC BY-NC-ND

Irritant contact dermatitis

Irritant contact dermatitis is also a reaction to an external agent that the skin comes into contact with. Unlike allergic contact dermatitis, irritant contact dermatitis is not an allergic reaction. Rather, it is the effect of a direct irritating or toxic agent on the skin.

Irritant contact dermatitis can also result from the use of products such as deodorants, antiperspirants, soaps, or hand washes. The rash may be red, rough, or scaly. In severe cases, blisters may appear .


Diaper rash is a rash that occurs in the moist areas of the skin folds. In addition to the armpits, it can also occur under the breasts, in the folds of the groin, and in the folds of the abdomen. The rash is also often accompanied by yeast , fungi, or bacteria that thrive in a humid environment.

Prevention focuses on keeping the folds dry. In the active state, anti-inflammatory agents are often recommended, as well as against the presence of organisms .

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


Erythrasma is a rash that occurs after an infection with the bacteria Corynebacterium minutissimum . In addition to the armpits, the rash can affect other areas with skin folds, such as folds in the groin, under the chest, and in the spaces between the toes.

The rash appears reddish and / or brown, and the skin may show slight wrinkles. It is known for its coral-red fluorescence when illuminated with a wooden lamp. This rash is usually treated with erythromycin .

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

Corporal ringworm

Ringworm is often called ringworm , although it is caused by a fungus, not a worm. Depending on the location of the fungal infection, the name changes. There are different types of fungi that cause this infection of the upper layer of the skin.

The rash may appear red and the edges may be accentuated. The edges may also be slightly raised and there may be a thin layer of scales near the edge of the rash. This infection is most often treated with topical antifungals, some of which are available without a prescription .

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

Black acanthosis

Acanthosis nigricans appears as dark, velvety patches in skin folds, such as the armpits, groin, and around the neck. It could be due to obesity, diabetes or insulin resistance, hormonal changes, certain medications, or cancer.

Although the condition is generally not treated directly, correcting the underlying condition can help improve the appearance of these areas.

Frequently asked questions

  • You are likely allergic to one or more of the fragrances or essential oils used in your deodorant. Propylene glycol, a preservative and moisturizer, can also cause breakouts. Your allergist can do an allergy test, but it can be difficult to find the exact irritant. A non-allergenic product can help.

  • Intertrigo is a common rash under the armpits that causes burning and red maceration (when the skin becomes soft and irritated from excess moisture). It can be caused by fungus or friction between hot, moist skin folds. It is more common in people with diabetes or people who are overweight.

  • Maybe. Acanthosis nigricans is a skin disorder in which areas of the skin darken and become velvety. The armpits are an area where they usually appear, but they can occur in other places as well. The condition is caused by too much insulin in the blood, so this is a possible sign of diabetes.

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