I have an underarm rash (both arms). I have been using Cortaid maximum strength cream?

If the rash keeps coming back, you might want to try an antifungal cream. I would recommend something OTC like what is used for jock itch or athletes foot. Often a rash in an area that is moist is a fungal infection. Lotrimen cream is a good one to try. Use it as directed for as long as it is directed. If it is fungal you should begin to see the rash clearing. If the OTC antifungal doesnt work then I suggest you see your Dr or a dermatologist for advice. Be sure to keep the area clean and as dry as possible. Wash the area with soap and water prior to applying the antifungal cream. When you are home resting keep your arms raised often to keep the area dry and exposed to the air.