I think maybe the original diagnosis may be wrong.

Bed bugs give big red welts... not a rash.

But scabies...now this can be contracted from an old (infected) mattress. The main lesions can be lost in a global body rash that is quite itchy and sometimes painful. (I have seen it in some patients who get it all over themselves).

There are viral exanthems that can cover the whole body in response to a viral illness. If you type "viral exanthem picture" into Google you can find these. My husband had one while he was in the army and came home with it, for a leave. However, he claimed that it did not hurt or itch.

I would make sure you are eating enough foods high in EFAs, like flax oil and salmon (omega-3s). These are the main oils that repair the skin. Also in males, it is common to be zinc deficient. If you do not eat seafood or much chicken or meats, you could be low in zinc. Skin issues often happen in zinc deficient patients. This can be tested for by a blood test called the zinc/copper ratio.
There are vitamins with mixtures of things to improve skin.
One is called ACES with zinc. (by Carlson). But these can only do so much if you do not provide the essential fats for them to work on.