To prevent underarm rashes from developing, it's important to understand what causes them in the first place. One way to avoid heat rash is to simply not go outside in hot, humid weather. If you have to be outside, try not to overexert yourself, and wear loose-fitting clothing made of porous fabric. Also, don't use powders, creams or ointments on your skin -- they can clog pores and interfere with perspiration [source: Mayo Clinic]. The preventive measures for friction rashes are the same as for heat rash -- keep your underarms dry and wear light, loose-fitting clothing [source: Selden].
If you suspect that skin care products or household chemicals are causing your rash, the best way to avoid contact dermatitis is to identify the offending product and discontinue its use. Determining the culprit may require some trial and error, but it's best to start with your deodorant. Other items that may cause underarm rash include laundry detergent, soap, shampoo and lotions. If your symptoms don't improve, or if you're unable to identify what's causing your rash, see your physician -- he or she can test for a specific allergy [source: Mayo Clinic].
Once you've succeeded in identifying and eliminating the cause of your underarm rash, it's time to focus your attention on treating its symptoms. Keep reading to learn more.