Although most fish are known to be allergenic, cod and salmon tend to cause more allergic reactions than other varieties. Rounding out the list of allergenic fish are anchovies, tuna, mackerel and sardines.
If you discover that you're allergic to one type of fish, there's a good chance you're allergic to another type, too [source: FAI]. In any case, try to avoid seafood restaurants in general. Though you might order something off the landlubbers side of the menu, cross-contamination in the cooking process can still trigger an allergic reaction. Furthermore, beware of Worcestershire sauce and Caesar salad dressing, both of which usually contain anchovies.