Hello, I can understand your concern for red lines. It appears from your description that it is “Urticaria or commonly known as hives. Urticaria is a frequent situation caused by bursting of allergy producing cells known as mast cells . It can be due to certain aggravating factors present in the environment. As the chemical inside mast cells is released it produces the red lines which you have mentioned. There can be multiple factors producing this condition which are included in day to day life. Some times it is really difficult to find one exact cause. In your case you try and correlate with exercises, hot climate,spicy food. So it is better to stay away from the offending factors. The best effectual treatment for this is by oral anti histamine like loratadine under medical advice. It is one of the drugs which do not have any side effects and can be taken for long term usage. Do not scratch or rub the skin as it can lead to further provocation. All the best.