allergic

Before cerelac i was feeding him Gerber oatmeal and Gerber rice with banana and apple. Both no reactions. But when i gabe him cerelac, his mouth area became red and bumpy. But it goes away within 2 hours. Im not sure if he's allergic to either the milk solid or broccoli. Carrot and spinach are fine because i fed him the puree before and he was okay.