Hello, I can understand your concern for the redness and burning sensation after exercising. After reading your query I can male out that you are suffering from Cholinergic Urticaria . Cholinergic Urticaria is a common condition caused by bursting of allergy producing cells known as mast cells due to certain aggravating factors. In your case it aggravated by exercises. Due to sudden exercising the chemical inside them is released it produces a rash which you have mentioned. There can be multiple other factors producing this condition which are included in day to day life and some times it is really difficult to find one exact cause. In your case you are correlating it with exercises as the main cause. The long term effective treatment for this is by oral anti histamine like loratadine under medical advise. It is one of the drugs which is not having any side effects and can be taken for long term usage. In my patients I suggest them to take the antihistamine round the clock and especially 2 hours before the exercises. All the best.