Hazard Identification

Fin fish is one of the commonest causes of food allergy. It is a real food allergy resulting in IgE-mediated symptoms, which is not to be confused with the toxic reactions that occur after histamine ingestion from spoiled fish (which will usually cause a reaction in everyone who has eaten the fish).

The allergy is caused by ingestion of almost all fish because it involves a protein found in the muscle of the majority of fish species. Although not complete, the list of fish causing allergy includes cod, mackerel, herring, sardine, anchovy, bass, haddock, hake, plaice, sole, salmon, tuna, trout, Alaska Pollock, eel, catfish, perch, and carp. Although fin fish and shellfish allergies are not linked by a common allergen, individuals may be allergic to both types of seafood.

Allergenicity

The major fish allergen is parvalbumin, a protein that is conserved across all species of fish. As the parvalbumins are similar in all species, individuals allergic to one type of fish are likely to be allergic to all others. Parvalbumin is heat-stable and therefore, cooking is unlikely to remove the allergenicity from fish. In addition, other proteins in fish, apart from parvalbumin, have been shown to be allergenic. The designated allergen name for parvalbumin from cod is Gad c 1 (from the latin name for cod, Gadus callarias), and the designated allergen name for the allergen from salmon is Sal s 1 (from the official name Salmo salar). A few people who are allergic to fish also react to frog, as frog muscle also contains the protein parvalbumin.

Allergy to cartilaginous fishes also exists, but it is possible that there may be differences between these allergies and allergy to bony fish. The cartilaginous fishes include sharks, rays, dogfish and skate.

Prevalence

The prevalence of fish allergy varies, but it is generally thought to affect between 0.1 and 0.2% of the population. Both children and adults are affected, and fish allergy generally persists throughout the lifetime of an individual. Fish allergy is more prevalent in countries and parts of the world where fish constitutes a major part of the diet.

Hazard Characterisation

Effects on health

As with most allergens the severity of the reactions varies depending upon the sensitivity of the subject and on how much of the allergen is consumed.

The first symptoms are generally itchiness and sensitivity of the mouth and throat, which can be followed by other reactions, such as:

• Nausea, vomiting, stomach pains and diarrhoea.
• Hives, itching, swelling and reddening of the skin.
• Eczema, asthma and hay fever, accompanied by runny and itchy eyes and nose.
• Swelling of the airways.
• Anaphylactic shock.

Dose-response

Doses as low as 5 mg of cod have been reported to elicit an allergic reaction. Allergic reactions to fish have also been reported after inhalation of allergens in the steam from cooking fish, and after kissing someone who had previously consumed fish. Cross contamination from frying oil containing minute amounts of fish protein is also a problem. Manual handling of fish can also cause eczema or asthma in sensitive individuals.

Management of fish allergy

Once a diagnosis of fish allergy has been confirmed, the only way to successfully manage the allergy is by complete avoidance of fish in any form, and fish-derived ingredients. As one of the recognised major allergens, fish should always be labelled on pre-packaged foods in the EU and the US.

The following foods may contain hidden fish: surimi, pâté, Worcestershire sauce, Caesar salad dressing, oyster sauce, tapenade, pizza toppings, kedgeree, caponata, bouillabaisse, gumbo, paella, fruits de mer, frito misto (mixed fried fish dish), fish sauce (Nuoc Mam and Nam Pla), gentleman's relish, sushi, and animal fat. Some fish or animal oils may also contain minute amounts of fish protein. Gelatine obtained from fish skin and bones and used in foods is not considered a problem for fish-allergic consumers.

Special care should be taken by people allergic to fish when they eat out in restaurants, as cross-contamination of foods can easily occur, for example, from the frying oil.

Sources of Further Information

Published

Bush R.K., Hefle S.L.
Food allergens.
Critical Reviews in Food Science and Nutrition, 1996, 36 (Suppl. S), 119-163

Poulsen L.K., Hansen T.K., Norgaard A., Vestergaard H., Skov P.S., Bindslev-Jensen C.
Allergens from fish and egg.
Allergy (European Journal of Allergy and Clinical Immunology), 2001, (56), supplement 67, 39-42

On the web

The InformAll Database
http://foodallergens.ifr.ac.uk/food.lasso?selected_food=5020

The Anaphylaxis Campaign
http://www.anaphylaxis.org.uk/information/print_common_food_al.html