The rash is a yeast rash that happens in warm, damp places. So try to keep it from being damp. I wear Lane Bryant Lightly Lined bras, they have some absorbent padding and the fabric that covers and cushions the underwire is thick and absorbent. Don't use baby powder, they make it with corn starch now and it'll just feed the yeast and make everything worse. In the summer I only wear my bras once (sometimes twice if I haven't been out in the heat and sweating a lot) and then I wash them on the delicate cycle in hot water, with a splash of bleach. Yes, that is very damaging to my expensive bras but I'd rather look for sales and replace my bras more frequently than deal with a miserable itchy rash under my breasts. I think Lane Bryant is still having their buy 2, get 2 free sale. I stock up then (when I can afford it) and I always have a rotation of 6 or more "good" bras, as well as a few that are looking worse for wear. Even with all the abuse my bras take with this cleaning ritual, they still last me more than a year; that should tell you how durable Lane Bryant bras are. I'll warn you that they have unique sizing though, I'd recommend stopping in at a store to try on your size to make sure it fits the same.