Do you break out in an itchy rash or develop itchy pink welts when you exercise? If so, you might have exercise urticaria. This is a common problem that can range from mild to debilitating. Exercise urticaria is triggered when immune cells, called mast cells, release histamine, causing the pink welts and intense itch. It’s thought to be the result of exertion and changes in your skin’s temperature. Once you develop the itchy rash, it’s difficult to treat. So the best defense against exercise urticaria is to take an oral anti-histamine, such as loratadine, about 30 minutes prior to working out.