It is not uncommon for people to have problems when eating fish, but most of the time these reactions are due to food poisoning and not an actual allergy. It is estimated that only about 4 out of 1000 people are truly allergic to fish.
One example of fish poisoning is called Scombroid fish poisoning, which results from eating fish that has not been refrigerated properly during transport. When the fish is left in warm temperatures, bacteria grows and produces an accumulation of a chemical called histamine. The bacteria is killed during the cooking process, but the histamine is still present on the fish. Once the fish is ingested, the accumulated hisatmine results in symptoms very similar to an allergic reaction which is why it is often mistaken for a fish allergy. An allergy test, performed by an allergies, can help differentiate between a true fish allergy and food poisoning.
There is no cross- reactivity between fish and shellfish (lobster, crab, shrimp, oyster,..) - so most people who are allergic to fish are not allergic to shellfish (or vice versa). However, because these 2 types of seafoods are often stored and prepared in the same area, there is a risk of contamination and it is therefor best for individuals allergic to fish (or shellfish) to avoid seafood restaurants.
Avoid foods that contain:
These foods may contain fish:
One should also be careful when eating fried foods (fries, chicken) if the same oil has also been used to fry fish.
People allergic to fish should avoid taking Omega-3 fatty acids made from fish oil. Instead, they should take Omega-3 fatty acids from walnuts, flax seeds, and flax seed oil.
Carrageenan, often used as a stabilizer or thickener in food, is a red algae and does not need to be avoided by fish allergic individuals.