It's unusual to get chafing or rashes from wearing pads. When you're wearing a pad, make sure you're wearing firm fitting underwear. Not tight, just snug. It shouldn't let the pad move around much at all. The pad shouldn't be rubbing against your skin. If you do have an allergy to the pad it would irritate you all the time, not just during exercise. If you think you might have an allergy to pads talk with your pharmacists about hygiene products made from different materials.