This article has been reviewed by Andrew Moore, MD, FAAAAI
Shellfish, including shrimp, lobster, oysters and more, are often touted for their health benefits. But for millions of Americans with shellfish allergy, a tiny bite of these foods can cause a severe reaction. If you have a food allergy such as shellfish, your immune system overreacts to a particular protein found in that shellfish.
Most people with one shellfish allergy are allergic to other species within the same class. For example, if you are allergic to crab, you may also be allergic to lobster, shrimp and other crustaceans. Likewise, if you are allergic to clams, you may also be allergic to other mollusks, such as mussels or scallops.
It is a myth that shellfish allergy means it is unsafe to receive iodine dyes. If you have a shellfish allergy, you can most likely safely get radiocontrast medical procedures, unless you have a separate allergy to them.
This myth originated in the 1970s from a survey of patients who reported prior reactions to contrast media. Among those who replied that they had a reaction, 15% also stated they were allergic to shellfish. It is important to note that this was not confirmed with any testing. After that report, physicians tried to make the connection and hypothesized that iodine was the reason for this suspected cross reactivity. However, iodine is not an allergen. It is present inside our bodies and too small to start an allergic reaction on the allergy cells in the body. Interestingly, iodine is also not the cause of allergic reactions to shellfish, which is caused by muscle proteins called tropomyosin. So, concern for allergic reactions to contrast media in people with shellfish allergy has been a myth all along, but unfortunately one that continues to impact physicians and patients alike to this day.
Another misconception is that shellfish-allergic patients cannot take glucosamine. Glucosamine is normally safe to consume because it is made from shells, not the protein that causes allergy to shellfish.
Shellfish allergy is more common in adults than children. This is probably due to our eating habits. Because young children don’t typically eat shellfish, this allergy may not be apparent until later in life.
As with other food allergies, avoiding contact with shellfish is the only sure way to manage your symptoms.
Many people who think they are allergic to shellfish may actually be intolerant to it. Some of the symptoms of food intolerance and food allergy are similar, but the differences between the two are very important. An intolerance to shellfish can make you feel miserable. An allergy to shellfish can result in symptoms of anaphylaxis (an-a-fi-LAK-sis), a life-threatening allergic reaction.
An allergist / immunologist has advanced training and experience to determine if you are intolerant or allergic to shellfish and help you manage your condition.
Find out more about food allergies.
Find out more about hellfish allergy and radio contrast myths.