I would seriously consider getting your son on MIchild - It's basically medicaid, but it's there so that no child needs to be without insurance. After my daughter was born and my husband lost his job when she was 2 weeks old, we filled out the necessary forms and the insurance was really good. We took her to the Beaumont Medical Center Children's Clinic. Well, we no longer have that insurance as my husband has a real good job now with wonderful insurance but it's nice to now that option was available and was there when we needed it.
Do you think maybe your child has eczema or is allergic to something? For temporary relief I would suggest Aveeno Anti-Itch Moisturizing Lotion. My daughter has eczema and multiple food allergies, so I've been down the "mysterious rash" road.
Hope this helps!
God bless,
C.