Vanillin

Vanillin is rated 0 by SIGHI as 'vanillin (synthetic)' — well tolerated, no symptoms expected at usual intake — and no mechanism letter stands beside it. The vanilla POD sits one line away at 1 with two uncertainty marks, which is the comparison worth having: what separates them is that a pod is dried plant tissue and vanillin is one molecule taken out of it. That list reports a perceived compatibility and not a measured content, so it places this additive without giving it a figure.

Vanillin carries no tyramine, and SIGHI's own notation is what says so: that list marks an A against every entry it holds to carry other biogenic amines, and it sets no letter at all against 'vanillin (synthetic)'. The blank is a judgement and not an oversight: the same page marks the vanilla pod one line above, so the list was looking.

Vanillin carries no salicylate, which is worth saying because the vanilla pod does and the two share a name. Vanillin is one molecule, 4-hydroxy-3-methoxybenzaldehyde — a phenolic aldehyde, not a salicylic acid derivative. What raises the pod on this axis is everything ELSE a dried plant tissue carries: its secondary metabolites, of which vanillin is only the one that smells.