Hazelnut

Hazelnut is notable for salicylate, nickel, oxalates and histamine. Clear on tyramine, sucrose, FODMAPs, lactose, oligosaccharides, sorbitol, fructose and gluten.

Yes — hazelnut is high in salicylate. Hazelnuts are high in salicylates, and the spreads and pralines made from them deliver a far bigger portion than a handful of nuts would.

Yes — hazelnut is high in nickel. Hazelnut is one of the nuts named among the very high-nickel foods, and nothing published ranks it against the other tree nuts. If nuts are being reintroduced one at a time, this is the one to leave for last.

Yes — hazelnut is high in oxalates. Hazelnuts are high in oxalate, and the published totals for them disagree between tables more than for most nuts. The skin is often said to hold most of it — that is documented for the almond, and no measurement compares a blanched hazelnut with a whole one. Rubbing the skins off after roasting follows the reasoning rather than a figure.

Hazelnut contains moderate levels of histamine. Hazelnuts are usually sold roasted and skinned, and both operations shorten their shelf life - the skin is where much of the antioxidant sits, and removing it leaves the oil less protected. A hazelnut that tastes of paint is oxidised, and that is the state to avoid here. One amine has been measured across this group and it does not sort the nuts the way the elimination lists do: Yilmaz found serotonin running from 0.05 to 155 micrograms per gram raw across twelve nuts, hazelnut among them, with roasting cutting the maximum to a tenth. The abstract publishes only the extremes, so there is no hazelnut figure in it — which is worth saying rather than implying one. Amounts vary by brand and recipe, so always check the label of the exact product.