Both my sons had eczema from birth that was helped only when I cut out the allergen. I say helped because it didn't go away entirelyeven when I cut things out. Having eczema is often part and parcel of having food allergies. They've both mostly outgrown the eczema, but my oldrr son now has asthma, which also comes in hand with food allergies.I had a peek at your blog (hope it isn't too stalkery) and saw the pic of your son's reaction. That's pretty serious and widespread. Watch for other more 'subtle' reactions like unusual lethargy, coughing, runny nose, sneezing, vomiting, diarrhea, stomach pain, wheezing, blue or swollen lips. If one of mine had your hives with ANY other symptom, I would have given an epi. In fact, I know for many that full body hives is enough to warrent an epi.
In terms of othef foods, obviously avoid dairy and any other foods you've seen reactions to. Stay with whole foods, and avoid anything packaged. So plain meats, steamed veggies, plain fruit. At least until you've seen your allergist. Do you know if it's a pediatric allergist? Iwould highly recommend one. A website that has saved me many times is kidswithfoodallergies.org. Extremely useful, with helpful forums and lots of info. Hope that helps!