When my lo was 3 months my grandma gave him cinnamon (bad yes I know!! :/) he got red blotches around his mouth I asked the dr they said it may just be irritating his skin and try again when he gets older hes almost 11 months and was eating apple sauce with cinnamon in it and his face started blotching again. He has no other symptoms he's playing fine could it still just be irritating his skin?
I had a friend allergic to cinnamon. It's possible he's allergic.
It's pretty common, happens a lot and isn't that big of a deal if it's just skin irritation. Watch his poops, he'll likely rash easily, but if it doesn't seem to bother him otherwise, there's no reason he can't have it.