Reactions in people with severe fish allergies can be triggered by small quantities of fish, occasionally left behind on food utensils or dishcloths. Doctor Brostoff, a leading expert on food allergies, refers to a case where a young gentleman fell victim to his girlfriend’s kiss; she had eaten fish half an hour beforehand. As a casualty officer, I once had to resuscitate a lady from near death, even though she was highly vigilant about her severe prawn allergy. Although she avoided any contact with prawns, she was caught unawares by the aroma of prawns being fried in an open wok in a restaurant and collapsed because of anaphylaxis, a severe allergic state.

Crustacean shellfish (prawns, lobsters, shrimps and crabs) contain various peptides (small protein molecules) that can cause allergic reactions. Various other chemical agents, such as preservatives, are often added to fresh fish or shrimp / prawn cocktails, and can be the cause of allergic symptoms in individuals who are not allergic to fish or crayfish.

Fish reared in fish farms frequently contain traces of antibiotics, and may trigger allergic reactions in individuals with severe antibiotic allergies. Some types of fish, especially tuna and mackerel, contain high levels of histamine, and can therefore cause pharmacological food intolerance. The histamine does not come from the fish itself, but from bacteria, which naturally degrade the fish, if not kept below certain temperatures. Sushi, (sometimes not as fresh as claimed), is often responsible. Fish affected in this way may have a sharp, peppery or metallic taste, and usually smells more “fishy” than normal.

Cross sensitivity between different species of fish occur. This means that individuals who experience allergic symptoms caused by one type of fish, may experience the same symptoms when exposed to a different species of fish. The following forms of cross sensitivity exists within the seafood group:

All the fish in the main group that are commonly eaten are bony fish, and share a special protein known as parvalbumin, known to provoke allergic reactions. If you are allergic to this protein, you have no choice but to avoid all other species of fish as well. Other forms of fish allergy exist, and many can be identified by performing individual RAST tests. (Consult your doctor for further information).

A very large group, consisting of many families. Crabs, lobsters, crayfish, shrimps and prawns are included in this family. Most patients react to all forms of crustaceans.

A very large group, consisting of many families. Mussels, cockles, winkles, oysters, clams, scallops, squid, cuttlefish, octopus and snails are included. Most patients react to all forms of molluscs.