Break out in rash after being out in intense heat/sun?

Ever since we hit the summer months over here in Iraq (apr+) every time I go outside in PT uniform (shorts and a tshirt) I break out in an extensive rash on both arms and legs where the skin is exposed. I went to the Army doc who claimed it was eczema but, the eczema regimen they prescribed doesn't help the condition at all, besides I've never heard of eczema suddenly appearing after sun exposure? Plus my skin isn't dry. The rash seems to be spreading like wildfire, and I dont have the time or patience to go back to the army doc who will just tell me to bugger off. Zinc Oxide helps a bit, but its rather difficult getting it out here, anyone have suggestions on what it can possibly be and a good method to get rid of it? I know for a fact it is not sand fleas.