What Causes Recurring Itchy Red Marks All Over Body?

I have red marks that look like scratch marks but aren t on my back and also it stings and goes away temporarily with hot showers and ice but keeps coming back. Have been taking Benadryl but no relief. What s going on?? Some pain but does not travel past my back. And it itches occasionally, stinging is like tiny needles pricking all over that area. I m only 21 years old.