I would say no - I have no food allergies or intolerances, but my skin will get rashy on contact with tomatoes, citrus juice or oils, cooking/massage/essential oils, the sap from fruit or plants like figs...

Nai is right about testing allergens first with touching them to the lips, but a rash isn't conclusive, whereas swellling or systemic reaction is. Lip skin functions very differently from the rest of our skin. It's like a cross between skin and mucous membrane like we have inside the mouth.

If you wanted to test it, I'd put a glob of wet vitabrit on his forearm for a bit and see if the rash comes up there. Then you could go on the work out if it's the milk, or the wheat, or the preservatives in it, etc...