Seafood allergy occurs in about 1% of the population and is more common in adults than children. It is more common in area where there is a high consumption of fish such as Scandanavia. Seafood allergy is an important cause of anaphylaxis.
Signs and symptoms of the allergy occur within minutes of ingestion. They range from GIT symptoms – nausea, stomach cramps , diarrhoea to skin symptoms such as rashes and angiodema (swelling ) and may also present with respiratory symptoms such as wheezing or shortness of breath.
There are 3 main groups of seafood: fish , molluscs and crustaceans. Crustaceans encompasse prawns, shrimps , lobster , crayfish and crab. Cross reactivity between the different groups can occur.
Diagnosis rests on a careful history combined with blood or skin prick tests. It is important on the history to distinguish true seafood allergy from poisoning by bacteria that are present in the fish due to inadequate refrigeration. These bacteria break down and release histamine which may cause similar symptoms. Game fish such as Yellow Tail and Tuna are often implicated as they contain a high content of red meat.
Anisakis Simplex is a parasitic worm that lives in the flesh of fish. If fish is properly cooked at a temperature of more than 60 degrees the worm is destroyed but infection occurs if fish is undercooked. Symptoms are usually gastrointestinal with cramps , nausea and vomiting. Symptoms due to Anisakis are intermittent . Diagnosis is confirmed by testing for IgE antibody levels to the Anisakis.
Algae toxins may also contaminate shellfish and fish and cause neurological symptoms.
Lastly, preservatives in shellfish may cause wheezing and skin rashes so these may need to be taken into account.
This blog is taken from an excerpt of an article from the journal of Current Allergy and Clinical Immunology June 2016 .
