I got an itchy, red rash in my armpits from a new deodorant I tried out. It did nothing to battle sweat, so my armpits in just a few days were so constantly wet that all the heat and perspiration led to an irritating, itchy rash in my armpits that just drove me crazy. Many things can cause an armpit rash, the most common ones being from shaving, dryness, excess perspiration (check), and a reaction to a certain laundry detergent or anti-perspirant (deodorant). Check again.
Once you have identified what caused your rash, it’s easy to treat. Make sure you bathe daily to eradicate bacteria from your armpits and body, and make sure your armpits are completely dry before applying hydrating lotions to both soothe your skin and treat the condition causing the rash. If shaving is the cause, avoid shaving your armpits for a few days to allow the skin to heal (and you may consider changing out your razor).
Once your armpits have been cleansed and dried (a mild soap will do when bathing- rinse thoroughly), apply a gentle moisturizer without a lot of chemicals, like Aloe Vera, Vitamin E, or tea tree oil, all of which work to hydrate the skin, fight bacteria, soothe the skin’s itchiness, and regenerate skin growth so the area can heal. You want to avoid overly processed lotions and perfumes and dyes, so go as natural as you can (I used Aloe Vera- I keep it in the fridge to make it ultra soothing).
When putting on anti-perspirant (if anti-perspirant is the cause) apply it lightly, and change anti-perspirant brands if your anti-perspirant gave you the rash. Don’t rub the anti-perspirant on vigorously; rather, dab the product on to avoid irritating the rash further.
Wear cotton, loose fitting clothing to allow your armpits to breathe. If sweating is causing your armpit rash, try to keep them dry as possible (I put toilet paper under my arms to absorb sweat a few times a day) to avoid irritating the rash further. Make sure that you don’t sweat off the lotion or oil that you place in your armpits (in extreme cases of sweating, hydrocortisone cream works as well because it doesn’t sweat off as easy- I’ve had success with it).
The problem should clear up in just a few days, so long as you are keeping dry, keeping your armpits moisturized, bathing regularly to avoid irritation and wearing cotton, loose clothing. My rash cleared up in just 48 hours after I switched deodorants. If your problem persists, consult a doctor to rule out infection or other issues.