M.D.
I'm not sure exactly what your question is, but my infant broke out in eczema on his face when he was exposed to a food he was allergic to (it was cow's milk in his case). He also had terrible diaper rash after the exposure. When I eliminated that, his eczema and diaper rash went away.
If I were you, I first wait until his system is completely settled down - no rash and tummy is not upset. Then try something different. My infants preferred baby oatmeal cereal instead of baby rice cereal. You might try that - and only give that for at least 2 weeks - before trying to add anything else to his diet. If he reacts to that also, then wait another month before trying anything else. He might need more time before he's ready, and that is totally ok. Breastmilk and formula provide all the nutrition your baby needs until he is 12 months old. The cereal is only for practice at eating, not nutrition.