Seafood Allergy

Seafood allergies are usually a life-long problem. People are usually only allergic to one seafood group. Seafood allergy does not increase the risk of iodine allergy. Some conditions (scombroid fish poisoning and Anisakis allergy) may seem like allergic reactions to seafood, but are separate conditions. Bad reactions may also occur after eating seafood infected or tainted by algae-derived neurotoxins (ciguatera and paralytic shellfish poisoning).

SYMPTOMS

Many allergic reactions to food are mild. Mild symptoms may be limited to hives or swelling in one area. The most dangerous symptoms are:

  • Breathing difficulties. This may occur from breathing in seafood allergen fumes when food is being cooked or in seafood processing factories.

  • A drop in blood pressure (shock).

  • Anaphylaxis is a severe whole body reaction. This is the most severe form of allergic reaction.

Other symptoms include:

  • Swelling of the face or throat.

  • Dizziness.

  • Difficulty thinking.

  • Intense sense of fear.

  • Tightness in the chest.

  • Vomiting.

  • Diarrhea.

TYPES OF SEAFOOD

There are many types of seafood. The major groups of sea life that trigger allergic reactions are:

  • VERTEBRATES

  • Scaly fish (salmon, cod, mackerel, sardines, herring, anchovies, tuna, trout, haddock, John Dory).

  • INVERTEBRATES

  • Crustaceans (prawns/shrimps, lobster, crab, crayfish, yabbies).

  • Mollusks.

  • Shellfish (clams, mussels, oysters, scallops).

  • Cephalopods (octopus, cuttlefish, squid, calamari).

  • Gastropods (sea slugs, garden slugs, snails).

As a rule, patients allergic to one group of seafood can usually tolerate those from another. Seafood allergy is most common in communities where seafood is an important part of the diet, such as Asia and Scandinavia. Sensitivity is more common in adults than children.

Occasionally, intense cooking will partially or completely destroy the triggering allergen. This may explain why some patients allergic to fresh fish are able to tolerate salmon or tuna in a can.

AVOIDING THE ALLERGEN IS AN IMPORTANT PART OF MANAGEMENT.

Complete avoidance of one or more groups of seafood is often advised. It may be difficult to achieve in practice. Accidental exposure is more likely to occur when eating away from home. This is most true when eating at seafood restaurants.

OTHER POTENTIAL SOURCES OF ACCIDENTAL EXPOSURE AND CROSS-CONTAMINATION INCLUDE:

  • Seafood platters (best avoided).

  • Asian foods in which shellfish can be a common ingredient or contaminant (prawns in fried rice or soups).

  • Food may be rolled in the same batter or cooked in the same oil as seafood (take-out fish and chips).

  • Anchovies (fish) in Caesar salads and as an ingredient, or Worcestershire sauce.

  • Contaminated barbecues.

  • Fish extracts are also occasionally used to remove particulate matter from some beverages such as wine and beer. This process is called "fining."

SEAFOOD ALLERGY AND IODINE ALLERGY ARE UNRELATED.

Even though seafood is a rich source of natural iodine, allergic reactions to seafood proteins have a different mechanism to that of iodine. Iodine can be found in topical antiseptics and x-ray contrast agents. Patients allergic to seafood are not at an increased risk of allergic reactions to iodine. Those with iodine allergy are not at increased risk of seafood allergy.

SEEK IMMEDIATE MEDICAL CARE IF:

  • You have difficulty breathing, or you are wheezing or have a tight feeling in your chest or throat.

  • You have a swollen mouth, or have hives, swelling or itching over your body.

  • You feel faint or pass out.

  • You develop chest pain or a worsening of the problems which originally caused you to seek medical help.

If you have eaten seafood and develop problems or symptoms that seem unusual for you, seek advice from your caregiver. If the problems are severe, call your local emergency medical service.