Pickled herring

Herring, like mackerel and sardines, is naturally high in histidine — the amino acid bacteria convert into histamine. The pickling process gives that conversion plenty of time to happen.

• Fermentation risk — the brining and curing stages of pickling create an environment where histamine-producing bacteria thrive, often resulting in very high final histamine levels

• Vinegar doesn't help — pickling brine is acidic, but that doesn't neutralize histamine that's already formed; it's essentially preserved along with the fish

Fresh herring prepared and eaten the same day is a very different proposition for people who are sensitive.