This Month's Feature Review:

Seafood Allergy (Bony Fish, Crustacean and Molluscs)

Vincent St Aubyn Crump

Food anaphylaxis is now the leading single cause of anaphylactic reactions treated in emergency departments in Westernised countries. In the US, it is estimated that there are 29,000 anaphylactic reactions to foods treated in emergency departments and 125-150 deaths each year.

Seafood (scaly fish, crustaceans and molluscs) is one of the most common causes of food allergy. In adolescents and adults, peanuts, tree nuts, fish and shellfish account for approximately 85% of true food allergies.

Higher prevalence of seafood allergy is found in the countries where seafood is a staple part of the diet, like Scandinavian countries, Spain and Japan.

Seafood is potent allergens in sensitised individuals and cause life-threatening adverse reactions that are usually life-long. Extreme sensitivity to minute quantities of fish is occasionally noted, and even exposure to fumes of fish being cooked is enough to precipitate reactions in certain individuals.

The Mollusc group includes three different classes of seafood with species such as Abalone, oysters, mussels, and squid (Calamari).
The second group, the Crustacean, includes the rock lobsters ("crayfish"), prawns, crabs and shrimps; and the third important group of seafood includes all the common edible fish, such as Hake, Cod, Snapper, etc. Cod is the most frequently reported cause of fish allergy, but reactions to other fish such as haddock, herring, sprat, halibut, plaice, mackerel, trout and salmon are well recognised. Very often patients are only allergic to certain species but are able to eat other seafood species without problems.

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New and Interesting Allergy Studies:

Occupational asthma in a seafood restaurant worker: cross-reactivity of shrimp and scallops

Detection and quantisation of raw fish aeroallergens from an open-air fish market

IgE reactivity against a cross-reactive allergen in crustacean and mollusca: Evidence for tropomyosin as the common allergen

Surimi: Something fishy

Occupational asthma in a seafood restaurant worker: cross-reactivity of shrimp and scallops

David W Goetz, MD, PhD and Bonnie A Whisman, MS

This is an interesting study because it shows that seafood can cause allergies by ingestion, inhalation and contact.

It presents the case of a restaurant seafood handler with IgE-mediated occupational asthma and contact urticaria to both shrimp and scallops.

It concludes, "Seafood allergens aerosolized during food preparation are a source of potential respiratory and contact allergens. Shrimp and scallops demonstrate significant cross-reactivity. These findings confirm that the primary cross-reactive allergen of shrimp (phylum Arthropoda) and scallops (phylum Mollusca) is&"

Reference: Annals of Allergy, Asthma, & Immunology 2000; 85:461-466

Detection and quantisation of raw fish aeroallergens from an open-air fish market

Adela V. Taylor, MD and Richard T Jones, BS

This is another study that supports the fact that inhalation of seafood is an important route for sensitisation and producing allergic symptoms. This is important for occupational and non-occupational exposure to seafood. In Madrid and here in New Zealand, patients with IgE-mediated fish hypersensitivity have had reactions (wheezing, asthma, urticaria and rhinitis) after exposure to fish odours in an open-air fish market and on fishing boats.

The study compared air samples from an open-air fish market in Madrid with an outdoors residential area, and concluded, "By using air sampling and an immunochemical analytic technique, fish allergen is detectable in the air of an open-air fish market. Avoidance of a food allergen, such as fish, should include preventing exposure to aerosolized particles through inhalation in relevant environments".

Reference: J Allergy Clin Immunol 2000; 105:166-9.

IgE reactivity against a cross-reactive allergen in crustacean and mollusca: Evidence for tropomyosin as the common allergen

Patrick S.C. Leung, PhD et al

This study looks at the well known cross-reactivity between molluscs and crustaceans in shrimp-sensitive individuals and concludes "The allergic epitopes (reactive part of an allergen) on tropomyosin are conserved among invertebrates including not only shellfish but also insects. This latter observation suggests that persons sensitive to shrimp should undergo further study for potential cross-reactive inhalant or ingested insect sensitivity".

Reference: J Allergy Clin Immunol 1996; 98:954-61.

Surimi: Something fishy

Jon J. Musmand, MD et al

Surimi (derived from a fish) is a common hidden seafood allergen.

"This case report demonstrates that a patient allergic to fish may have a significant allergic reaction to surimi. In a previous study, Helbling et al investigated the allergic potential of surimi in a group of 30 adults allergic to fish. Fifty percent (15 of 30) of the group had positive skin test responses to both pollack and surimi extracts. Further, 30% of the group had positive RAST responses to surimi and pollack. The authors demonstrated cross-reactivity between a surimi-derived pizza topping and several fish species, including pollack."

Reference: JACI September 1996. Volume 98. Number 3