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

Trout Allergy Test: Allergen Exposure

Trout is the common name for a number of species of freshwater fish in the family Salmonidae (salmon family), and they are closely related to salmon and char. Trout are classed as an oily fish, and are an important food fish for humans. They are distributed throughout North America, northern Asia and Europe, and have been introduced to Australia and New Zealand.

While trout are relatively bony compared to other food fish, they are prized for the flavour of their flesh and their nutritional value. As a popular food they are widely farmed, but can also be caught in the wild through rod and line fishing or ice fishing.

They are sold both fresh and frozen, either as whole fish or fillets. They are usually served either grilled, oven baked or pan fried, and are also often preserved by smoking. Smoked trout has a texture similar to that of smoked salmon.

Trout is a good source of vitamin B1, vitamin B6 and potassium and a rich source of protein, omega-3 fatty acids, vitamin D, vitamin B3, vitamin B12, phosphorus and selenium.

Trout may also be used as an ingredient in omelettes, kedgeree, fishcakes, fish pies or tarts and in salads.

According to the British Nutrition Foundation, trout contain one of the lowest amounts of dioxins (a type of environmental contaminant) of all oily fishes.

Trout Allergy Test: Allergen Description

No specific allergens present in trout have been characterised, although a number of proteins have been identified.

Trout Allergy Test: Potential Cross-Reactivity

Species within groups of fish, like Gadiformes (examples: codfish and hake) and Scombroid fishes (examples: mackerel and tuna) seem to share allergenic components. The overlap of allergen specificity between the groups seems to be moderate or even small.

Cross-reactivity within the family Salmonidae can therefore be expected, which includes salmon, trout, chars, freshwater whitefishes, and graylings.

Trout Allergy Test: Clinical Experience

Studies have found some cod-sensitive children to have IgE antibodies to trout. IgE antibodies to trout were also measured in a group of patients suffering from atopic dermatitis.

Sensitisation to fish allergen is common. Fish, including trout, is a potential cause of food allergy and atopic dermatitis. Immediate allergic reactions may follow ingestion of even minute amounts of fish.

Symptoms can include oral allergy syndrome, generalised urticaria, facial angioedema and anaphylaxis.

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.

It has been reported that some fish allergic persons can exhibit allergic symptoms due to the steam (airborne allergens) from cooking fish.

Other reactions

Acute anisakiasis as a result of the larvae of the fish parasite Anisakis simplex may occur following ingestion of undercooked or raw trout which has been wild-caught.

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.