Fish allergyL27.2

Type I- Food allergy to various fish allergens. Clinically important is the distinction to a so-called "fish poisoning", a toxin-induced reaction. After chicken protein and raw vegetables, fish is the most important cause of food allergies (sensitization to parvalbumin).

Sensitisation to fish products is playing an increasing role as an occupational disease in the fish processing industry.

• Classification of different clinically relevant fish species: European freshwater fish (the fauna of European freshwater fish comprises over 500 species from over 13 families):
• spikehead fish (Atheriniformes)
• Eel-like (Anguilliformes)
• Perch-like (Perciformes)
• Carp-like (Cypriniformes)
• Codfish (Gladiformes)
• Pikelike (Esociformes)
• Herringlike (Clupeiformes)
• Mullet species (Mugiliformes)
• Needles of the sea (Syngnathiformes)
• Sticklebacks (Gasterosteiformes)
• Sturgeons (Acipenseriformes)
• Tank cheeks (Scorpaeniformes)
• Flatfish (Pleuonectiformes)
• Seawater fish:
• Butte (Bothidae)
• Codfish (Gladiformes)
• Fan and spear fish (Istiophoridae)
• Finger fish (Polynemidae)
• Hair tails (Trichiuridae)
• Herringlike (Clupeiformes)
• Marks and tunas (Scombridae)
• Medusa fish (Stromateidae)
• Flat fish (Pleuronectiformes)
• Swordfish (Xiphiidae)
• Anchovies (Engraulidae)
• Common hip (Paralichthyidae)
• Plaice (Pleuronectidae)
• Turbot (Scophthalmidae)
• Tongue (Soleidae).

Fish contain a large variety of proteins; only a few are defined as allergens.

Cod: Major allergen is Gad c1, a 12 kDa protein(parvalbumin) found in cod and the first fish allergen to be isolated. Parvalbumin is a family of calcium-binding proteins found in muscle cells. About 70% of fish allergy sufferers are sensitised to parvalbumin. The similar amino acid sequence of gad c 1 and parvalbumin in other fish species leads to a high proportion of cross sensitizations.

The chicken-fish syndrome is based on cross-reactivity between parvalbumin, aldolase and enolase in fish and chicken (Massalme EG et al. 2017).

Further known fish allergens (Identified single allergens of the different fish species) are fish species according to IUIS Allergen Nomenclature Sub-Committee):

Herringlike fish

• Herring (Clupea harengus Atlantic herring)
  • Clu h 1 beta-parvalbumin: see below Parvalbumin; determination potentially useful as a representative for a whole fish family

• Pacific sardine (Sardinops sagax, Pacific pilchard)

  • Sar sa 1 Beta-parvalbumin

Carp-like fish

• Carp (Cyprinus carpio, Common carp)
  • Cyp c 1 beta-parvalbumin: marker allergen for an entire fish family

Cod-like fishes

• Baltic cod (Gadus callarias, Baltic cod)
  • Gad c 1 beta-parvalbumin
• Cod (Gadus morhua, Atlantic cod)
  • Gad m 1 beta-parvalbumin: see below Parvalbumin
  • Gad m 2 Beta-enolase: 63% of the sensitized react to the beta-enolase of cod. Most of these patients do not react to parvalbumin.
  • Gad m 3 Aldolase A: 50% of the sensitized patients react to cod aldolase

Perch-like fish

• White-throated perch (Oreochromis mossambicus, Mozambique tilapia/white-throated perch of the cichlid family)
  • Ore m 4 Tropomyosin: Data situation is still unclear. Cross-reactions against tropomyosin of shrimps have been proven.

• Orange roughy (Sebastes marinus, Ocean perch, redfish, snapper)
  • Seb m 1 Beta-parvalbumin
• Tuna (Thunnus albacares, Yellowfin tuna)
  • Thu a 1 beta-parvalbumin
  • Thu a 2 Beta-enolase
  • Thu a 3 Aldolase A
• Swordfish (Xiphias gladius, Swordfish)
  • Xip g 1 Beta-parvalbumin

Salmonid fish

• Keta salmon (Oncorhynchus keta, Chum salmon)
  • Onc k 5 Vitellogenin
• Atlantic salmon (Salmo salar, Atlantic salmon/)
  • Sal s 1 beta-parvalbumin
  • Sal s 2 Beta enolase
  • Sal s 3 Aldolase A
• Rainbow trout (Oncorhynchus mykiss, Rainbow trout)
  • Onc m 1 beta-parvalbumin

Flatfish

• Megrim (Lepidorhombus whiffiagonis, Megrim, Whiff, Gallo, megrim of the turbot family)
  • Lep w 1 beta-parvalbumin

Other fish species

• Barramundi (Lates calcarifer (barramundi/predace, from the family of giant perch)
  • Lat c 1 beta-parvalbumin

In the case of an allergy to carp, those affected also cross-react to other fish (e.g. cod, perch, salmon). In this case it is generally recommended not to consume fish. Individual heat-labile proteins (40-85 kDa) have been found in sole, hake and monkfish).

• Oral intake causes gastrointestinal problems, urticaria, oral allergy syndrome, angioedema and occasionally asthma attacks.
• In the case of inhalation, rhinitis, rhinoconjunctivitis allergica and asthma are the main symptoms.
• Intensive skin contact with fish can lead to allergic contact urticaria.

See below food allergy. A specific immunotherapy for the treatment of fish allergies does not exist, as the risk of anaphylactic side effects cannot be estimated. A strict maternity leave is recommended for those affected. Caution is advised with products such as paella, Worcester sauce (may contain fish gelatine).

• The consumption of fish in Germany has risen steadily in recent years. The most popular types of fish in Germany are herring, plaice, salmon, pollack, redfish, mackerel, trout and tuna. Fish is becoming increasingly important as a source of protein and especially because of its content of unsaturated fatty acids.
• The frequency of allergy triggering also depends on local eating habits. In Norway, cod allergies dominate, in Spain pike and turbot allergies.
• About 40% of allergy sufferers have an isolated allergy to a specific fish species; the risk of the fish allergy sufferer reacting to another species is 50% (!).
• Monoallergies are probably based on species-specific allergens that have not been sufficiently characterised so far.
• In principle, freshwater fish such as perch, trout, pike, carp, tench or pike-perch are rather well tolerated. Saltwater fish, on the other hand, (e.g. shark, halibut, cod, redfish, plaice, pollack, tuna) more often trigger allergic reactions.
• Fish proteins have a strong allergenic potency. Even small amounts (possibly the inhalation of vapours from cooked or dust-dried fish can trigger anaphylactic reactions). Most allergens are heat-stable (cooked or fried fish is also not tolerated). Fish allergens can be a "hidden allergen" in pigs and poultry fed with fishmeal. Even through breast milk allergic reactions can be triggered in sensitized infants. Many fish allergy sufferers also acquire an allergy to seafood (no cross-reactions!).
• Relatively often, occupational allergies are also observed in the fish processing industry. For example, 11.9% of the employees in a salmon-processing company developed asthma due to a fish allergy. Herring was found to be the trigger of occupational allergic type IV contact dermatitis with cross-reactivity to other fish of the order of Clupeiformes (sardine, anchovy).

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