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In the U.S. alone, about six million people are allergic to shellfish. That’s 2 percent of the entire population. This means that you aren’t alone if you’re living with shellfish allergies or if someone in your family is.
Being diagnosed with a food allergy can mean that you need to absorb a lot of information quickly in order to keep yourself or your family member safe. Here are the basics of what you need to know about being allergic to shellfish.
An allergy to shellfish means that proteins in shellfish trigger a significant immune system response in your body, which can be life-threatening in some people. There are two groups of shellfish out there. Mollusks include creatures like snails, oysters, scallops, abalone, mussels, squid, octopus, and clams. Crustaceans include shrimp, lobster, prawns, and crabs. It’s more common to be allergic to crustaceans than to mollusks.
You can be allergic to one or to both. Some people who can’t eat crustaceans can eat mollusks, for example, and vice versa. In addition, some people can eat certain crustaceans but not others, like being allergic to crab but not shrimp.
However, if you have an allergic reaction to any shellfish, mollusk, or crustacean, you’ll need to test the other ones under medical supervision. Most allergy clinics will allow you to sample the food you’re testing in their office, where you can get urgent medical attention if you have a severe allergic reaction. It’s not safe to test these on your own.
In addition, it’s never safe to try shellfish again on your own once you’ve had an allergic reaction. If you want to try to reintroduce any shellfish, you need to do so only under the supervision of your healthcare team.
Shellfish allergies aren’t like some other allergies in that they more commonly develop in adults, rather than in children. In fact, 60 percent of people with shellfish allergies discovered them later in life, rather than in childhood. This may happen because children are less likely to eat shellfish, though that hasn’t been definitively established in research.
While it’s possible to outgrow a shellfish allergy, particularly if you developed it as a child, this is less common than it is with some other allergies. Allergies to shellfish proteins, along with allergies to fish, tree nuts, and peanuts, are more likely to be lifelong than allergies to soy, milk, and eggs, for instance.
Most of the time, an allergic reaction to shellfish will show up within several minutes to a few hours after eating them. However, in some cases, you may see a delayed reaction, which happens more than a few hours later.
You may experience symptoms that run anywhere from mild to severe. Allergic reactions can be hard to predict, and they may get worse over time. Even though you had a mild reaction once, you might have a more severe one later on.
Symptoms of a shellfish allergy may include:
A shellfish allergy can cause a severe allergic response called anaphylaxis. This is a reaction that involves your whole body. It can get worse very quickly and can be life-threatening if you don’t get treated right away. Symptoms of anaphylaxis include several that are listed above, including not being able to breathe, developing a swollen throat, feeling disoriented, and losing consciousness. Even if you haven’t had anaphylaxis before, you could have it the next time you’re exposed to shellfish. That’s why it’s important to understand the allergy and know how to treat it.
Getting the right diagnosis for a shellfish allergy can be harder than you might think. Because people have different symptoms and symptom severity, it can be hard to figure out what’s going on.
Your allergist might do a skin-prick test, where they introduce a tiny amount of shellfish into a small hole poked in your skin and see if you respond. They may also do a blood test, where they send a sample of your blood to the lab and expose it to shellfish proteins to measure the level of shellfish-specific immunoglobulin E (IgE) antibodies. Finally, they may have you do an oral challenge test in their office. You’ll try shellfish there, and they’ll monitor you to see how you respond, including giving you emergency treatment if you need it.
They’ll look at the results of these tests, plus your medical history and experience with shellfish, to diagnose your shellfish allergy. Your healthcare provider may do all of the allergy testing listed above, or they may choose one or two options, then see if they need to do more. Once you’re diagnosed, your doctor will help you get the treatment you need for your shellfish allergy.
The best way to treat a shellfish allergy is to avoid shellfish entirely. This means avoiding not only shellfish themselves but also anything that has shellfish products in it or has come into contact with shellfish (or might have) during the food preparation and serving process. This is called cross-contamination.
Shellfish are easier to avoid than some other foods because products that come from these animals aren’t likely to be hidden in other foods. In addition to not eating specific shellfish, you’ll need to avoid fish stock, sushi, surimi, and any seafood flavoring. You may want to ask questions before you eat any sort of seafood stew (like bouillabaisse), any imitation fish, or anything with cuttlefish ink, as these can contain shellfish, too.
Eating out in restaurants can be hard because the people you talk to don’t always know the details of what goes into every dish. In some restaurants, this can change based on what’s available and what the chef wants to add that day.
If you’re very sensitive to shellfish, you may not be able to eat in any restaurant where shellfish are prepared in the kitchen. That’s because minute amounts of the proteins that trigger your allergic reaction can be present in vapors in the kitchen. Even dishes that don’t touch shellfish and are prepared entirely away from them could get contaminated this way.
In addition to avoiding consuming shellfish, you shouldn’t touch or handle them, either. Some people have an allergic reaction simply to this kind of shellfish exposure.
If you have anaphylactic reactions to shellfish, you’ll need to carry epinephrine, or adrenaline, with you all the time. This is the standard, first-line treatment for an anaphylactic reaction, and delaying treatment can be life-threatening. Most people who live with any sort of food allergy, including one to shellfish, carry epinephrine auto-injectors (called EpiPens) with them all the time, just in case they need to use them.
Your doctor will teach you how and when to use your epinephrine. They’ll likely give you two doses, and you should always have both of them with you. An allergic reaction may require more than one dose. If you have any severe shellfish allergy symptoms, you should use epinephrine right away. Even if you aren’t sure whether to use epinephrine or an oral antihistamine, use your epinephrine because it’s better to use it and not need it than to need it and not use it. If your doctor has any other instructions for you, though, you should follow those instead.
If you use epinephrine, you also need to call for emergency help right away. Tell the person on the phone that you’ve used your auto-injector and that you may need more epinephrine from the emergency team that comes to help you.
On MyFoodAllergyTeam, people share their experiences with food allergies, get advice, and find support from others who understand.
How long have you lived with a shellfish allergy? Let others know in the comments below.
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