Seafood and Seafood Allergens


"Seafood"
  • General term that includes finned fish, crustacean, and mollusks
Vertebrate finned fish
  • All FDA-regulated manufactured food products that contain fish as an ingredient are required by U.S. law to list the specific fish on the product label.
"Shellfish"
  • Includes crustaceans and mollusks

Crustaceans
  • All FDA-regulated manufactured food products that contain a crustacean shellfish as an ingredient are required by U.S. law to list the specific crustacean shellfish on the product label.
Mollusks
  • Not considered major allergens under food labeling laws and may not be fully disclosed on a product label
Examples
  • Salmon
  • Tuna
  • Cod
  • Bass
  • Swordfish
  • Etc.
  • Barnacle
  • Crab
  • Crawfish (crawdad, crayfish, ecrevisse)
  • Krill
  • Lobster (langouste, langoustine, Moreton bay bugs, scampi, tomalley)
  • Prawns
  • Shrimp (crevette, scampi)
  • May also be found in
    • Bouillabaisse
    • Fish stock
    • Glucosamine seafood flavoring (e.g., crab or clam extract)
    • Surimi
  • Abalone
  • Clams (cherrystone, geoduck, littleneck, pismo, quahog)
  • Cockle
  • Cuttlefish, cuttlefish ink
  • Limpet (lapas, opihi)
  • Mussels
  • Octopus
  • Oysters
  • Periwinkle
  • Scallops
  • Sea cucumber
  • Sea urchin
  • Snails (escargot)
  • Squid (calamari)
  • Whelk (Turban shell)
  • May also be found in
    • Bouillabaisse
    • Fish stock
    • Glucosamine seafood flavoring (e.g., crab or clam extract)
    • Surimi
  • Note that the phylum Mollusca is categorized into Gastropoda (snails, abalone), Cephalopods (squid, octopus), and Bivalvia (scallops, mussels)
Allergens
  • Major allergen is beta-parvalbumin
    • Resistant to degradation by heat, proteolytic enzymes, chemical denaturation (nevertheless it is denatured by the canning process)
    • Concentration of parvalbumin may be higher in white flesh fish (e.g. cod) vs. darker flesh (tuna), therefore darker fish are considered to be less allergenic
  • Allergy to fish roe has been reported
  • Major allergen is tropomyosin
    • Heat stable
  • Other allergens include:
    • Arginine kinase
    • Myosin light chain (1 and 2)
    • Sarcoplasmic binding protein
    • Troponin C
    • Triosephosphate isomerase
  • Shrimp at allergen.org
  • Sensitization to a particular shrimp species (while tolerating others) can occur, presumably due to unique allergens
  • Major allergen is tropomyosin
    • Heat stable
  • Other proposed allergens include:
    • Arginine kinase
    • Hemocyanin
    • Myosin heavy chain
    • Amylase


Seafood Allergen Cross-reactivity



Differential Diagnosis

  • IgE-mediated allergy or infection by Anisakis simplexfish parasite
    • Cooking at temperatures for at least 20 min above 60°C or storage in industrial freezers is required to kill the parasite
    • Signs of anisakiasis depend on where in the GI tract the larva is deposited and may develop as a result of an inflammatory response to infection
  • IgE-mediated allergy to spices or other foods eaten with fish
  • Cross-contamination of food allergens
    • Fish contaminated with shellfish (and vice versa) during preparation (e.g. via shared utensils/cutting boards in restaurant kitchens)
    • Soy, milk, or other proteins added to canned seafood
  • Scombroid fish poisoning and other marine toxins:
Toxin-associated disease (toxin)
Location
Seafood affected
Symptom Onset
Symptoms
Ciguatera (ciguatoxins)
Most originate in tropics/subtropics
More than 400 species; predominantly reef dwelling tropical fish such as barracuda, moray eel, amberjack, grouper, mackerel, parrot fish, red snapper
30 min - 4 h
Gastroenteritis, neurologic, cardiovascular, fatigue and malaise
Paralytic shellfish poisoning (saxitoxins)
Primarily temperate climates, northeast and northwest coasts in United States
Most commonly bivalve molusks such as clams, oysters, and mussels
5 - 30 min
Neurologic - can progress to paralysis and respiratory failure
Neurotoxic shellfish poisoning (brevetoxins)
Southeast coast of United States, Gulf of Mexico, northern Spain, eastern Mediterranean, Japan, New Zealand
Shellfish (often mussels, clams)
30 min - 3 h
Gastrointestinal, neurologic, pulmonary
Diarrheic shellfish poisoning (okadaic acid, dinophysistoxins, pectenotoxins, yessotoxin)
Worldwide; major outbreaks in Japan, Scandinavia, France, Spain, Chile, Uruguay, Nova Scotia
Shellfish (often mussels, clams, scallops)
30 min - 6 h
Gastroenteritis
Pufferfish (tetradotoxin)
Most commonly in Japan; rare cases in United States
Pufferfish (Fugu)
10 - 45 min
Neurologic - can progress to paralysis and respiratory failure
Amnesic shellfish (domoic acid)
First recognized off the coast of Prince Edward Island, Canada
Shellfish (often mussels, clams, crabs), anchovies
15 min - 38 h
Gastroenteritis, neurologic
Possible Estuary- Associated Syndrome (PEAS)
Has been found in the Tar-Pamlico and Neuse River estuaries of North Carolina and in the Pocomoke River on Maryland's eastern shore
Various

Respiratory and eye irritation, neurocognitive



Diagnosis


Test
Shellfish
Finned fish

SPT

  • SPT with commercial extracts and fresh food typically has a high negative predictive value
  • SPT with commercial extracts and fresh food typically has a high negative predictive value
  • Boiled extracts may be more allergenic than raw, most commercial extracts include boiled shrimp allergen

In-vitro IgE assays

  • sIgE (Phadia ImmunoCap) to:
    • Various fish species (see catalog)
    • Beta-parvalbumin
      • rCyp c 1 - carp
      • rGad c 1 - cod
  • sIgE (Phadia ImmunoCap) to:
    • Various shellfish species (see catalog)
    • rPen a 1 - shrimp tropomyosin
      • In one study, sIgE to shrimp tropomyosin (via an ELISA method) was equally sensitive (~70%) but more specific (92%) than SPT (64%) or sIgE to whole shrimp (75%) in predicting positive shrimp food challenges in dust mite sensitized patients (but only 22% of patients had history of reaction to shrimp)
    • rDer p 10 - dust mite tropomyosin
  • ISAC to tropomyosins (Phadia ImmunoCap)
    • rAni s 3 - Anisakis
    • nBla g 7 - Cockroach
    • rDer p 10 - Dust mite
    • rPen a 1 - Shrimp
    • nPen i 1 - Shrimp
    • nPen m 1 - Shrimp

Oral Food Challenge

  • Results of OFC may be inconsistent due to species of seafood used, method of preparation (boiled vs. raw), incomplete digestion due to acid blocking medications, allergies only to specific components of the seafood (white vs. dark meat, crab shell, fish roe)
*



Shellfish Allergy Management (Sicherer)

Patient type
Management
Anaphylaxis (life threatening) to shellfish
  • Avoid ALL shellfish
  • Avoidance of finned fish is not necessary (unless patient also has an allergy to fish)
    • If choosing to eat finned fish, be aware of cross-contamination with shellfish during preparation
    • Avoid restaurants or prepare fish at home
Non-life threatening reaction to shellfish
  • Avoid specific type of shellfish that caused the reaction (e.g. shellfish A)
  • If ingestion of another type of shellfish is desired (shellfish B), consider further evaluation:
    • SPT to shellfish with commercial extract (consider fresh prick to prick), if negative, allow home ingestion (consider office ingestion or OFC), if SPT positive, avoid shellfish B (vs. cautious OFC)
    • If patient tolerated eating shellfish B at home afterreacting to shellfish A, may continue ingesting shellfish B
    • If allowed to eat another type of shellfish, be aware of cross-contamination during preparation; avoid restaurants, prepare shellfish at home
  • Avoidance of fish is not necessary (unless patient also has an allergy to fish)
    • If choosing to eat fish, be aware of cross-contamination with shellfish during preparation
    • Avoid restaurants, prepare fish at home



Finned Fish Allergy Management (Sicherer)

Patient type
Management
Anaphylaxis (life threatening) to fish
  • Avoid ALL fish
  • Avoidance of shellfish is not necessary (unless patient also has an allergy to shellfish)
    • If choosing to eat shellfish, be aware of cross-contamination with finned fish during preparation
    • Avoid restaurants, prepare shellfish at home
Non-life threatening reaction to fish
  • Avoid specific type of fish that caused the reaction (e.g. fish A)
  • If ingestion of another type of fish is desired (fish B), consider further evaluation:
    • SPT to fish B with commercial extract (consider fresh prick to prick), if negative, allow home ingestion (consider office ingestion or OFC), if SPT positive, avoid fish B (vs. cautious OFC)
    • If patient tolerated eating fish B at home after reacting to fish A, may continue ingesting fish B
    • Patients who react to fresh tuna/salmon typically tolerate them in canned form. If an individual has reacted to fresh tuna/salmon and is interested in eating them canned, additional SPT/OFC are suggested.
    • If allowed to eat another type of fish, be aware of cross-contamination during preparation; avoid restaurants, prepare fish at home. Be aware that up to 25% of fish in stores/restaurants may be mislabeled.
  • Avoidance of shellfish is not necessary (unless patient also has an allergy to shellfish)
    • If choosing to eat shellfish, be aware of cross-contamination with finned fish during preparation
    • Avoid restaurants, prepare shellfish at home
Reaction to canned fish only (fresh fish tolerated)
  • Allergy isolated to canned fish is rare
  • Some brands of canned tuna contain soy or milk proteins (and may apply to other canned fish)
  • Canned fish could be contaminated with shellfish during processing




Seafood Allergy Monitoring and Natural Course





References