Answer: Try switching antiperspirants. According to Debra Jaliman, M.D., a New York City dermatologist, clothing discoloration can result when chemicals in these products react with your body. If that doesn't help, you probably have a lot of bacteria in your sweat (everyone's contains bacteria; some people just happen to have more of it than others). To get rid of it, wash your underarms twice a day with an antibacterial soap like Dial, Hibiclens or Phisoderm (in addition to using a new antiperspirant). If the problem persists after several weeks, ask your dermatologist about topical antibiotic treatment. In some cases, a stronger prescription antiperspirant such as Drysol may also help by further curbing sweat.
Originally published in Fitness magazine.