It was Methyl Paraben. I looked it up again, I guess it is not HIGHLY allergenic, but there have been reported cases of an allergic reaction when ingested. This is probably what caused his reaction. Unless, of course, he could have had a reaction to the sweeteners? I'm not sure if they are at all allergenic. Anyway, this is what I found on Wikipedia on Methyl Paraben:
Methylparaben is readily absorbed from the gastrointestinal tract or through the skin.[1] It is hydrolyzed to p-hydroxybenzoic acid and rapidly excreted without accumulation in the body.[1] Acute toxicity studies have shown that methylparaben is practically non-toxic by both oral and parenteral administration.[1] In a population with normal skin, methyl paraben is practically non-irritating and non-sensitizing; however allergic reactions to ingested parabens have been reported.
But who knows, the ingredient list is confusing, and wouldn't surprise me if it was something else.
