Milk Allergy?

Alex has been struggling with excema on his cheeks and chin since the fall - about when he started to eat table foods. He has always had a weak tummy - even when breastfed, he'd throwup after feedings and this continued when we switched to formula. I asked the pediatrician about it at his 6 month visit but he didn't seem too concerned - he thought it could be related to volume - in other words, he was just eating too much. He suggested trying soy formula for a few days to see if it makes a difference, I never did. Bad Mommy!
We started transitioning to whole milk about 2 weeks ago. Alex continues to spit up after nearly every bottle - and it stinks even worse than the formula - sour milk - yuck!
Last night I purchased some soy milk. He had his first full bottle this morning - and guess what? No spit up! AND no rosy cheeks and chin! Later this morning, I gave him some Quaker oatmeal - peaches and cream. Soon after, his face got red. I pulled out the box and checked out the ingredients: 'Contains milk and soy'. Okay. I think I am going to have to record everything he eats and see how he reacts. What fun!
So much for being the laid back and calm one... Alex has decided to become difficult in ways much different from his sister!
Meanwhile, neither Bobby nor I have an allergy of any kind. Nor does Robert... I wonder where this comes from - and I hope it is soon outgrown!