Cod is a food which may result in allergy symptoms in sensitised individuals.

Cod Allergy Test: Allergen Exposure

The cod is a large fish of around two metres in length. It is one of the most important food fish globally, and as well as being eaten fresh is available frozen, salted, smoked or canned.

It has a mild flavour and a dense, flaky white flesh which is moist when cooked. The liver can be canned or used to manufacture cod liver oil, which is an excellent source of vitamins A, D, E as well as omega-3 fatty acids.

Cod may be considered a hidden allergen, as it is sometimes present in commercially prepared foods such as cured meats. It may also be a contaminant of cooking oil, kitchen utensils and surfaces, or storage containers.

Cod Allergy Test: Allergen Description

Several IgE-reactive allergens spanning a wide molecular-weight range have been detected in Cod extracts.

Cod Allergy Test: Potential Cross-Reactivity

Species within groups of fish such as Gadiformes (examples: cod and hake) and Scombroid fishes (examples: mackerel and tuna) seem to share allergenic components.

A study evaluated the cross-reactivity among 9 common edible fish – cod, salmon, pollock, mackerel, tuna, herring, wolffish, halibut, and flounder. Cross reactivity was demonstrated between herring and wolffish, whereas halibut, flounder, tuna, and mackerel displayed the lowest cross-reactivities.

Cod Allergy Test: Clinical Experience

Sensitisation to fish allergen is common. Fish, and especially cod, is a common cause of food allergy and atopic dermatitis, in particular in countries of the northern hemisphere and Asian countries.

Contact with cod through ingestion or through the inhalation of cooking vapours has resulted in allergic symptoms, including oral allergy syndrome, generalised urticaria, facial angioedema and anaphylaxis.

A UK study of 76 children documented a total of 125 reactions to 23 different food allergens. The top five food allergens in descending order were egg, peanut, tree nut, cow’s milk and cod, together accounting for just under 90% of all reported reactions.

In another study of Italian children with food allergies, about 18% had IgE antibodies to Cod and two-thirds had clinical manifestations upon inhalation or ingestion of the fish.

Wheezing and life-threatening bronchospasm have been reported.

Anaphylaxis has been reported – a fatal anaphylactic reaction occurred in a fish-allergic patient who ate fried potatoes cooked in the same oil in which fish had been cooked.

Oropharyngeal itching and swelling occur as the first symptom, always preceding the onset of any accompanying symptoms.

Contact with fresh raw cod has also resulted in allergic dermatitis, urticaria and anaphylaxis.

Immediate allergic reactions may follow ingestion of even minute amounts of fish.

Because patients react to both cooked and raw fish, it is assumed the allergens are heat-resistant. However, more recent studies indicate that patients may react differently to processed food and that allergic reactions may be species-specific.

Other reactions

Acute anisakiasis as a result of the larvae of the fish parasite Anisakis simplex may occur following ingestion of undercooked or raw cod.

Symptoms can include abdominal pain, nausea, vomiting, abdominal distention, diarrhea, blood and mucus in stool, and mild fever. Allergic reactions with rash and itching, and infrequently, anaphylaxis, can also occur.