Kefir

Kefir is made by fermenting milk with a complex mix of bacteria and yeasts, and several of those microbes may produce histamine as they work.

• Fermentation variability — histamine levels in kefir can vary between batches and brands depending on the specific cultures used and fermentation conditions; commercial kefir is typically refrigerated by the time of sale, but the histamine developed during fermentation remains

• Compared to plain milk — fresh, unfermented dairy contains little to no histamine; the fermentation step is what raises kefir's histamine level substantially

Those curious about fermented dairy may find plain yogurt from a single-culture starter somewhat easier to tolerate, though individual responses vary.