Red splotches on arms and chest after exorcise, or stress or adrenaline. all the time after showers and sometimes after sex. is this bad?

Dermatographism: some get red raised areas on their body after exercise and after rubbing the skin. I believe this is histamine induced from the mast cells. Either,way, do not worry about it. It may be harder to allergy test you due to this reaction. If you have allergies and want to get tested, you will need to get your blood drawn. Good luck and feel better.