Eel

Eel is rarely eaten plain — it's almost always smoked, cured, or served in sauce, and each of those processes adds histamine on top of what the fish naturally contains.

• Smoking and aging — these processes involve time and microbial activity, both of which allow histamine to build up. Smoked eel is considerably higher than fresh eel

• Sauces and marinades — eel dishes like unagi often involve soy-based glazes, which are themselves fermented and add another layer of histamine

Fresh, plainly prepared eel would be a lower-histamine option, but it's rarely available in that form outside of specialist fishmongers.