What Is Seafood Allergy? Causes And Symptoms

Email to Your Friends

All About Seafood Allergy

Mostly an adult-onset, seafood allergy is your immune system's response to a protein found in shellfish muscles called tropomyosin. Symptoms range from mild ones like swelling or skin rashes, wheezing, repetitive cough, and stomach cramps to fatal ones like a sudden drop in blood pressure or difficulty in breathing. Your best bet is to stay alert by scrutinizing food labels and keeping your medication handy.

Seafood has a lot of nutritional value and benefits for health. Collectively used for both fish and shellfish like shrimp, prawns, squid, octopus, crabs and lobsters, seafood is loaded with a lot of minerals, lean proteins and good fats like omega fatty acids.1 Let’s not forget, it tastes delicious! While seafood maybe a delicacy of choice for some, it is a cause of deadly allergies for a lot of people.

What Is Seafood Allergy?

These allergies mostly begin in the adult phase of life and can continue forever. Chances of an adult growing out of a fish or shellfish allergy are minuscule. Though it is mostly adult-onset, children are not exempted from them either. Seafood allergies are a serious health concern, with recurrent and sometimes severe reactions. According to a study, as many as 6.6 million Americans were suffering from seafood allergies in 2004.2

Causes Of Some Common Seafood Allergies

The major identified allergen in fish is parvalbumin, a calcium ion-binding protein.3

Tropomyosin, which is a muscle protein, is a major allergen in shellfish, particularly crustacea (shrimp, prawns, crayfish, lobster, crab) and mollusks (scallops, snails, clams, octopus, oysters, squid). In some individuals, when their antibodies sense tropomyosin or any other allergen in their bodies, they trigger the release of histamine and other such chemicals to attack it. This leads to symptoms that can range from mild to life-threatening.4

Arginine kinase (an allergen in tiger shrimp and white shrimp), hemocyanin and amylase are some other seafood allergens.5

Apart from these seafood proteins which act as allergens, eating seafood can trigger allergic reactions if it is contaminated in one way or the other. Some such allergic reactions include Scombroid fish poisoning, Anisakis Simplex, Metabisulfite reactions, etc.6

But it’s not always eating seafood that can bring about an allergy. It can also be triggered by inhaling cooking vapors and handling seafood!7 However, such reactions are not likely to be severe like anaphylaxis. They usually only cause minor breathing difficulties.8

How About Fish Oil Supplements?

Fish oil supplements are popular as a source of omega-3 fatty acids. In the process of making the capsules, it goes through various levels of filtration and purification and is often considered safe.9 But if you get a severe allergic reaction from having seafood, it is better to look for other omega-3 supplements with no fish by-products or take some tests to rule out any reaction before having them.

Various Seafood Allergy Symptoms

Allergies usually work their way through the gastrointestinal tract and the reactions usually manifest themselves about 10 minutes after consumption. Skin rash or hives, swelling, vomiting, and diarrhea are the common symptoms. Stomach cramps, indigestion, wheezing, shortness of breath, repetitive cough, dizziness, weak pulse, tight and hoarse throat with trouble while swallowing are some other allergic reactions to seafood.10

But the most dangerous symptoms are breathing difficulties or a drop in blood pressure. This is a life-threatening allergic reaction known as anaphylaxis or anaphylactic shock.11

How Do I Know If I Have Seafood Allergy?

If you’ve had any of these reactions to any type of fish or shellfish, chances are that you are allergic to it. But fret not, as there are ways to figure out what’s safe and unsafe for you.

Skin Prick Test

This is the most common test as it provides a rapid, safe and inexpensive method for screening patients. However, it is not considered very precise with a positive predictive value of only 50 percent. These tests are particularly challenging in figuring out fish allergies due to the large volume of edible fish species out there.12

RadioAllergoSorbent Test Or RAST

This is a blood test to determine a variety of foods you can possibly be allergic to. Though less sensitive than skin tests, the RAST or RadioAllergoSorbent Test is useful for certain cases like patients with severe skin diseases, patients who are sensitive to certain foods, and more.13

Oral Food Challenge

This is the gold standard in food allergy tests. The selection of foods to be tested by oral challenge is determined by the patient’s history, laboratory results, or sometimes both. For this test, you need to discontinue or minimize all anti-allergy medication for a couple of days as advised by the physician. This test is done on an empty stomach, introducing very small amounts of the foods that are suspected to cause allergies, often masked as other foods or blended with other foods. This is a time-consuming test with the physician fully prepared to handle reactions and the results are pretty accurate.14

Ways To Manage Seafood Allergies

Seafood allergy is tricky in that you could get exposed to the allergen accidentally since there are many food items in the market that could carry traces of seafood. If you have a seafood allergy or any food allergy for that matter, you know what it’s like to be on the wrong side of a reaction. You probably dream of the day when you can have the food item to your heart’s content without experiencing any unpleasantness.

Stay Alert, Keep Medication Handy

Unfortunately, the only sure shot way of staying away from allergic reactions is to strictly eliminate the allergen. Patients and their families must learn to scrutinize food labels. Buffets, parties, picnics, and cafeterias propose bigger challenges as there is often no clarity. For example, fish or shellfish stock may be used in some dishes and there may be no way to know it. There may be a medley of seafood like prawns, scallops and shrimp in a fried rice dish. In such cases of accidental exposure to allergies, remember to keep your medication handy. For mild allergies like skin hives, gastrointestinal reactions, and asthma, oral medication is prescribed. If you have serious allergic reactions like breathlessness and the life-threatening anaphylaxis, you will need antihistamines or an injectable pen with adrenaline.

Challenge Yourself

Food challenges can be repeated at set intervals to figure out if you’re still allergic to the food item. However, in most cases, seafood allergies are permanent.15

Immunotherapy

Another not-so-common treatment for allergies is immunotherapy. The immune response to the allergen is altered in this therapy by carefully exposing the individual to increasing doses of the allergen. Immunotherapy may then result in desensitization (temporary) or tolerance (non-reactivity to the allergen for longer periods) to the allergen.16

Seafood allergy is more common than you think. It’s safer to be armed with enough precautionary measures before venturing out to eat.

References   [ + ]

1.Seafood Nutrition, FDA.
2.Sicherer, Scott H., Anne Muñoz-Furlong, and Hugh A. Sampson. “Prevalence of seafood allergy in the United States determined by a random telephone survey.” Journal of Allergy and Clinical Immunology 114, no. 1 (2004): 159-165.
3.Hajeb, Parvaneh, and Jinap Selamat. “A contemporary review of seafood allergy.” Clinical reviews in allergy & immunology 42, no. 3 (2012): 365-385.
4.Lehrer, S. B., R. Ayuso, and G. Reese. “Seafood allergy and allergens: a review.” Marine Biotechnology 5, no. 4 (2003): 339-348.
5.Rahman, Anas M. Abdel, Robert J. Helleur, Mohamed F. Jeebhay, and Andreas L. Lopata. Characterization of seafood proteins causing allergic diseases. InTech, 2012.
6, 8, 11.Allergic and Toxic Reactions to Seafood, ASCIA.
7.Lopata, Andreas L., and Samuel B. Lehrer. “New insights into seafood allergy.” Current opinion in allergy and clinical immunology 9, no. 3 (2009): 270-277.
9.Mark, Barry J., Andrew D. Beaty, and Raymond G. Slavin. “Are fish oil supplements safe in finned fish–allergic patients?.” In Allergy and Asthma Proceedings, vol. 29, no. 5, pp. 528-529. OceanSide Publications, Inc, 2008.
10.Fish and Shell fish allergy, British Allergy Foundation.
12.Sharp, Michael F., and Andreas L. Lopata. “Fish allergy: in review.” Clinical reviews in allergy & immunology 46, no. 3 (2014): 258-271.
13, 14, 15.SAMPSON, HA. “Food allergy. Part 2: Diagnosis and management.” Journal of allergy and clinical immunology 103, no. 6 (1999): 981-989.
16.Chafen, Jennifer J. Schneider, Sydne J. Newberry, Marc A. Riedl, Dena M. Bravata, Margaret Maglione, Marika J. Suttorp, Vandana Sundaram et al. “Diagnosing and managing common food allergies: a systematic review.” Jama 303, no. 18 (2010): 1848-1856.

Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.

Email to Your Friends