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Suspcious of Shellfish Allergies? We Can Help
Shellfish Allergy Symptoms, Causes, and When to See a Doctor in New Orleans, LA
Dr. Reena Mehta is a board-certified allergist that can help you identify and navigate shellfish allergies in New Orleans, LA.
“Dr. Mehta has a great bedside manner and is great with our daughter. She helped us navigate the most up to date treatment options for food allergies in our 9 month old and dedicated one on one attention to us that went above and beyond the norm. She is professional and kind and has a genuine care for her patients. Highly recommend!“
– Parker Valergo, 2019
Symptoms
Allergy List
Testing
Treatment
Myths & FAQs
Shellfish allergy is a type of seafood allergy. It occurs when the body produces an immunological response to tropomyosin and other muscle proteins found in shellfish. Shrimp, crab, and lobster are crustacea, and they cause most shellfish reactions. Mollusks such as clams, mussels, oysters, and scallops can also cause shellfish allergy, but allergies to mollusks are less prevalent compared to allergies to crustacea. Shellfish allergy is an immunoglobulin E (IgE) antibody-mediated allergy. This means that when you ingest shellfish, your immune system overreacts by producing IgE antibodies which bind to mast cells. Once the shellfish protein allergen binds to the IgE antibody on the mast cell, the mast cell will release histamines that trigger allergy symptoms.
Shellfish allergy is different from fish allergy. You could be allergic to shellfish but not finned fish with a backbone such as salmon, trout, halibut, cod, or tuna. In contrast to a lot of allergies, most people develop shellfish allergies when they are adults, and shellfish allergies typically last for life.
How Common is Shellfish Allergy?
You can develop a shellfish allergy at any age and this is true even if you’ve previously eaten shellfish without issues. However, shellfish allergy appears to be more prevalent in adults than children and 60% of all individuals with shellfish allergy first became symptomatic in their adulthood. In the US, survey studies have attempted to further quantify the proportion of the population with shellfish allergy. In one study by Sicherer et al., the authors found that 1 in 50 Americans self-reported a shellfish allergy.
Shellfish allergy that is IgE-mediated can cause a variety of symptoms which usually appear within minutes to an hour of ingestion. Shellfish allergy symptoms include:
- Urticaria (hives), an itchy skin rash of raised red spots
- Angioedema, or swelling under the skin
- Anaphylaxis, which is when multiple body systems produce a significant immune response causing a rapid drop in blood pressure and possible circulatory shock that is life-threatening
- GI symptoms such as nausea, vomiting, cramping, and diarrhea
- Lightheadedness and fainting
Sometimes, patients can have shellfish asthma reactions. For example, when exposed to an environment where shellfish is cooking or being processed, vapors from the shellfish may induce asthma.
In addition, shellfish allergy symptoms can be triggered by exercise or exertion following ingestion. However, in the absence of intense physical activity, a person might be able to eat shellfish without any reaction.
Many foods contain shellfish products that can trigger an allergic response, some of which are especially popular here in New Orleans.
Crustacean Shellfish Foods
- Lobster bisque
- Lobster roll
- Crawfish boil
- Crab dip
- Crab cakes
- Crawfish boil
- Imitation crab
- Sushi
- Cocktail shrimp
- Shrimp scampi
- Shrimp chips
- Prawns
- Jambalaya
- Creole or Cajun gumbo
What About Imitation Crab Meat?
Imitation crab, also known as surimi or crab stick, was developed in Japan as a cheaper alternative to genuine crab. It is highly processed with Alaska Pollock being the main ingredient. However, imitation crab also contains 2% or less of natural King Crab meat and extracts of blue crab, snow crab, and lobster–making it problematic for individuals with shellfish allergy. Refined anchovy and sardine fish oil is found in imitation crab as well.
Molluscan Foods
- Calamari and squid
- Clam chowder
- Scallops
- Oysters
- Clams
- Mussels
- Escargot
- Oyster sauce found in Asian cuisine
Other Fish-Based Products
- Fish oil supplements (may contain trace amounts of shellfish proteins)
Shellfish allergy tests include skin and blood tests to help aid in the diagnosis of a shellfish allergy. However, neither test is conclusive because a positive result to a certain food does not always mean you will react to that food when you ingest it. In addition, neither the size of the wheal nor the numerical value of the IgE antibodies predicts how severe your allergic reaction to shellfish will be. Negative skin and blood tests are most useful because they can help rule out a shellfish allergy.
Skin Testing for Shellfish Allergies
Your allergist may perform a skin-prick test to evaluate for potential shellfish allergy. Small volumes of food allergens (and controls) are pushed into your skin with a sterile needle. After 20 minutes, the skin is re-examined for any wheals, rashes, or bumps. It is important to note that skin testing for crustacean seafood (shrimp, crab, lobster, etc.) may be falsely positive due to sensitization to arthropods like dust mites, spiders, and cockroaches.
Blood Testing for Shellfish Allergies
A blood test can measure the amount of IgE antibody circulating in the blood in reaction to the shellfish allergen versus other types of allergens. High levels of circulating IgE can indicate allergic reaction. Blood tests results are usually available within 1 to 2 weeks.
Elimination Diet and Oral Food Challenge
To definitively diagnose a food allergy, your allergist may ask you to temporarily eliminate specific foods that are suspected allergens from your diet for 2 to 4 weeks. If your allergic symptoms disappear during this time, then one or more of the eliminated foods was the allergen. If shellfish allergy is suspected, your allergist may ask you to consume a small amount of shellfish allergen in a supervised, medical setting. This is done to confirm an allergy or to verify you have outgrown one.
Lifestyle Modifications
There are several ways to manage a shellfish allergy. Most important is avoiding shellfish itself and also any foods that contain shellfish by carefully reading nutrition labels for ingredients.
Shellfish Allergy Medications
Some medicines can treat a shellfish allergic reaction. If you have a mild reaction to shellfish, your healthcare provider may prescribe you an antihistamine or corticosteroid to control symptoms. However, only epinephrine injection via EpiPen can treat a severe shellfish reaction like anaphylaxis.
Shellfish Allergy and Iodine
Patients with shellfish allergies do not have a significantly increased risk of allergic reaction to iodine, which is commonly used as an intravenous contrast agent or dye for medical imaging procedures. It is true that shellfish contain iodine as a result of iodine being leached from the soil and washed into oceans. However, iodine is not the substance in shellfish that causes allergy; rather it is the tropomyosin and other muscle proteins in shellfish that do. Additionally, research shows that patients with seafood allergy (shellfish and/or fish) are just as likely to experience a contrast reaction as a patient with some other type of food allergy or asthma. Overall, 85% of patients with seafood allergy (shellfish and/or fish) who receive IV contrast for an imaging procedure will not undergo an adverse reaction.
Glucosamine and Shellfish Allergy
Glucosamine supplements are taken for joint health and to prevent osteoarthritis. Glucosamine is typically extracted from a material (chitin) found in the shells of crabs, shrimp, and oysters. However, shellfish allergy results from exposure to the muscle proteins in shellfish flesh, not shells. As long as there is no cross contamination and the product is of high purity, it is unlikely that the shells used in glucosamine supplements contain the shellfish protein allergens that trigger a reaction. If you’re unsure about a specific supplement, your allergist can help you determine if it’s safe to take.
Shellfish Allergy and Collagen
Fish collagen, derived from the skin, scales, muscle, and bones of fish, is found in some nutritional supplements. Fish collagen supplements do not contain shellfish protein allergens and are unlikely to cause an allergic reaction. However, some supplements contain ingredients collectively referred to as “marine collagen,” which can be sourced from a variety of seafood, both fish and shellfish. Therefore, if you have a shellfish allergy, always read the labels on supplement bottles to verify if any of the ingredients came from the skin or muscle of shellfish, and consult your allergist if you’re unsure.
Does fish oil contain shellfish?
No. Fish oil supplements commonly contain fish including mackerel, anchovy, and sardine but not shellfish.
Does crawfish have iodine?
Yes, crawfish are a type of crustacean shellfish and contain small amounts of iodine.
Do scallops have iodine in them?
Yes, scallops are a type of mollusk shellfish and contain small amounts of iodine.
Is there iodine in shellfish?
Yes, shellfish do contain small amounts of iodine. However, iodine is not the allergen in shellfish allergy.
Can someone eat imitation crab if allergic to shellfish?
Likely not. This is because imitation crab typically contains 2% or less of king crab meat (shellfish) and also contains natural and artificial extracts of crab and lobster.
Can you have an allergic reaction to imitation crab?
Yes, it is possible. Imitation crab often contains both fish and shellfish ingredients.
Can someone eat calamari if they are allergic to shellfish?
No. Calamari contains squid, which is a type of molluscan shellfish categorized as a cephalopod.
Is crab a shellfish?
Yes, crab is a type of crustacean shellfish.
Can you be allergic to lobster but not crab?
Yes, it’s possible. However, most people with one shellfish allergy are allergic to other shellfish species within the same class. Crab and lobster are in the same class of shellfish (crustacean) and so most people are allergic to both.
Can you be allergic to shrimp but not crab?
Yes, it’s possible. However, most people with one shellfish allergy are allergic to other shellfish species within the same class. Crab and shrimp are in the same class of shellfish (crustacean) and so most people are allergic to both.
How do you know if you’re allergic to lobster?
GI discomfort or pain, wheezing or shortness of breath, throat tightness, cough, hives, swelling, itchiness, weak pulse, and dizziness after ingesting lobster are all symptoms of lobster allergy.
How do you know if you’re allergic to shrimp?
GI discomfort or pain, wheezing or shortness of breath, throat tightness, cough, hives, swelling, itchiness, weak pulse, and dizziness after ingesting shrimp are symptoms of shrimp allergy.
See a Shellfish Allergy Doctor in New Orleans
Suspicious of shellfish allergy or asthmatic reactions? We can help. Allergist Doctor Mehta has a reputation for developing strong relationships with her patients and being exceptionally attentive to their needs and concerns.
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