Understanding Fish Allergies

If you are allergic to one fish, chances are you are allergic to more

Fish
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Seafood is an important part of the American diet. Tuna, salmon, and Alaskan Pollock are the most common fish eaten in the United States, with the average person eating over 6 pounds of fish every year.

While a healthy source of protein, fish also can cause illness through allergic and nonallergic food reactions. In the United States, 1 in 1,000 children and 1 in 250 adults will have an allergic reaction to fish.

The major allergen responsible for fish allergy is a protein called parvalbumin, which controls the balance of calcium in the white meat of fish. Parvalbumins are very similar between different species of fish. If you are allergic to one species of fish, you're more likely to be allergic to other species of fish as well. Gelatin is another major allergen that is shared among species of fish. If you are sensitized to fish and then come into contact with or eat fish, an allergic reaction will occur, leading to allergic symptoms.

Determining If You Have a Fish Allergy

Fish allergy symptoms are similar to other food allergies. If you have a fish allergy, you will most likely experience symptoms within an hour of eating the dish. Common symptoms include generalized itching, hives and swelling, vomiting, and respiratory symptoms such as wheezing and chest tightness. In rare cases, fatal anaphylaxis may occur.

You may experience hives and itching when you touch raw fish but are able to eat cooked fish meat without having allergic symptoms. Proteins released into steam when fish is being cooked can also cause allergic symptoms like asthma and hay fever if you have a fish allergy. 

Getting a Diagnosis

If you experience allergic symptoms after eating fish, the next step is to get a diagnostic skin or blood test.

A positive result to either test will confirm you have a fish allergy; however, skin testing remains the best way to confirm you are allergic to fish. Blood tests, on the other hand, have the advantage of measuring the amount of allergic antibody your produce against fish. The level of allergic antibody to fish can be helpful in determining whether you have a true fish allergy, have outgrown the fish allergy, or may be sensitized to fish without experiencing allergic symptoms.

A form of food poisoning, called scombroid, can also cause symptoms nearly identical to an allergic reaction. This type of food poisoning involves eating spoiled fish containing large amounts of histamine. The symptoms of scombroidosis are virtually identical those of a true food allergy. If you have scombroidosis, allergy testing will come back negative since no allergic antibody is present.

Living With a Fish Allergy

Since the major fish allergens are shared among many species of fish, if you are allergic to one fish, you may want to avoid eating all fish. You should also avoid seafood restaurants, given the chance of cross-contamination. 

Fish proteins can also be hidden in certain foods, and therefore cause unexpected allergic reactions.

Anchovies can be found in Worcestershire sauce and Caesar salad dressing. Surimi, processed Alaskan Pollock, is used as a meat filler in a variety of foods including sausages, pepperoni sticks, “meatless” hot dogs, and imitation crab. Parvalbumin can also be found in frogs. Therefore, if you have a fish allergy, you'll also want to avoid eating frog’s legs.

While you shouldn't eat other fish products such as sushi, caviar, roe, fish oil capsules, and cod liver oil, you may be able to eat shellfish as they are not related to fish. However, the danger of cross-contamination between fish and shellfish exists, which can make dining out difficult and leave you open to an allergic reaction.

If you have a fish allergy, your treatment plan will include avoiding fish. If you happen to eat fish by accident, immediate treatment will be required. This often involves the use of injectable epinephrine. Mild reactions may be treated with oral antihistamines. Consider wearing a Medic-Alert bracelet listing your food allergy information, if you have a fish allergy. And don't forget to carry injectable epinephrine at all times. 

Source:

Wild LG, Lehrer SB. Fish and Shellfish Allergy. Current Allergy and Asthma Reports. 2005;5:74-79.

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