Because the armpit skin folds over onto itself and has a concentrated number of sweat glands, rashes in the armpit are common. Many rashes are due to the growth of fungus or bacteria, while others can arise from irritations. Determining the cause of the rash is the first step to treating it. Consult a doctor for an accurate diagnosis.
Mechanical Irritations
Some of the most common causes for armpit rash are irritation of the area. Because hairs grow in the armpit region, shaving can cause razor burn, the chafed, red rash that occurs when the top layer of skin is removed with a sharp blade. According to Dr. Evelyn Placek, a dermatologist from Scarsdale, New York, a hasty application of soap followed by a quick drag of the razor over delicate underarm skin can cause a nasty red rash. She recommends that people stop shaving their underarms. Short of that, she recommends dabbing on hydrocortisone cream to irritated areas, making sure the underarm is well-hydrated before shaving, and using an aloe vera-based shaving cream instead of harsh, drying soap to prep the area. It may be necessary to allow the area to rest before attempting to shave it again.
Chafing can also occur due to constant rubbing in the underarm area. Common culprits are too-tight shirts, t-shirts, and other clothing, as well as harnesses and other sports gear. These rashes often disappear once the irritation is removed.
Chemical Irritations
Chemicals such as those found in soaps, shaving cream, deodorants, even shampoos can affect the underarm, causing a rash known as contact dermatitis. According to Skin Sight, some of the most common causes of allergic contact dermatitis include synthetic fragrances and lanolin, both of which can be found in underarm products. Contact dermatitis produces a rash that is pink or red, elevated and extremely itchy.
Treating the rash often requires discontinuation of the offending product and repeated applications of topical steroids as well as oral doses of antihistamines.
While not technically a chemical, heat can also cause a red underarm rash. Pediatrician Alan Greene, M.D. recommends washing the affected area with acne cleansing pads, applying hydrocortisone in lotion form, and taking antihistamines to control the itch.
Infections
Because of its dark, warm, moist location, the underarm is especially prone to infections. When a rash is already present, the skin is even more susceptible to bacterial and fungal overgrowth. Intertrigo, erythrasma, ringworm, boils, and abscesses are all due to an infection by bacteria, fungus, or yeast.
Treatment for infections require an accurate diagnosis. Often a doctor can differentiate between the types of infection based on the appearance of the rash. Common treatments include antibiotics, oral antifungal agents and antifungal creams or ointments.
