There are many potential causes of armpit rash.
Friction Dermatitis
Friction dermatitis is a common rash. The friction created by skin rubbing on skin or clothing, also called chafing, can cause irritation.
Heat and excess sweating can contribute to chafing. Shaving also makes your underarms more vulnerable to damage from rubbing because it removes skin, adds Kathryn Durham, MD, an American Academy of Dermatology certified dermatologist with U.S. Dermatology Partners in Fort Worth, Texas.
Contact Dermatitis
Irritant contact dermatitis occurs when an ingredient or element of a product — such as cleansers, deodorants, or even clothing — disrupts the skin barrier, Dr. Farnsworth says.
It can be tough to distinguish between the two types of contact dermatitis, as they can look the same. The culprits, such as fragrance or preservative, also are often the same, Farnsworth says.
Fungal Infection
“Yeast infections are often bright red, with bright bumps and pustules at the periphery, and often have a pungent, ‘cheesy’ smell,” Farnsworth says.
Hidradenitis Suppurativa
Hidradenitis suppurativa is a skin condition that features painful lumps in your skin. The lumps resemble pimples and acne cysts and often appear in the armpits, inner thighs, or groin.
Folliculitis
Shaving sets the stage for folliculitis, a condition where bacteria enter hair follicles, causing them to become infected and inflamed, Dr. Durham says. Folliculitis appears as red or white pimple-like bumps; some are filled with pus.
Atopic Dermatitis (Eczema)
“Eczema loves skin folds, and armpits are one spot we might see it,” Durham says.
Inverse Psoriasis
A specific type of psoriasis, this condition leads to a painful rash in skin folds such as under your arms, which see a lot of friction, Durham says.
- Alcohol use
- Smoking
- Stress
- Obesity
- Genetics
- Vitamin D deficiency
Some Cancers
Armpit rash is a fairly rare symptom of some cancers, but there are links.