Every time i sweat or get out of a hot shower, white whelps form on my chest and back and itch really bad. what is this and how can it be treated?

Reaction: Your body reacts in the hot shower by releasing histamine and other substances which cause this allergic type response. Try taking an antihistamine like benadryl(can cause drowsiness) or claritin(nondrowsy before taking the shower or try taking a colder shower to see if you can prevent the allergic reaction. An allergist is best qualified to evaluate and treat you for this problem.