Ok, the only things I could think of with trace amounts of dairy were wheat toast and crackers. He has dry toast every day for breakfast and crackers maybe every other day. Neither of these have dairy, but they both have soy and wheat ingredients. Also, since he's on soy formula, I assumed it would be alright if he had tofu, so he's been having that for the last few days.
He's been eating toast for breakfast for quite a while. So, I'm not convinced that is the culprit. I'll cut out the tofu and see what happens.
Sometimes I can be pretty thickheaded when it comes to figuring this stuff out. Can you believe that I just realized as I've been typing, that he's been vomiting for the last few days and he's started to have tofu in the last few days? AARRGGHH!