Is vomiting an allergic reaction to a food?

My LO had grapes (pureed) for the first time today. He generally takes solids really well in terms of tastes and textures. After I gave him a few spoon fulls he forcefully threw up after gasping like he couldn't breathe. After he threw up he seemed to be perfectly ok. Is this an allergic reaction? I don't think he choked because it was a thin puree and he has taken thicker purees and finger foods with no problem.

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