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From salmon to shrimp to scallops, many people love seafood. But unfortunately for some seafood lovers, there’s a chance of developing an allergy to shellfish and fish. Even though they both fall into the category of "seafood," fish and shellfish are biologically different, so fish will not cause an allergic reaction in someone with a shellfish allergy, or vice versa.
A seafood allergy, like every allergy, is when your immune system identifies something you come in contact with as harmful. When you have an allergy, and eat fish or shellfish, your immune system releases histamines, which then cause your allergic symptoms.
Fish and shellfish allergies are uncommon, but serious: An allergy to seafood can result in anaphylaxis—a life-threatening allergic reaction.1 Many people who develop a seafood allergy do so as an adult—60% of shellfish allergies and 40% of fish allergies began in adulthood—and their reactions can be severe.2 These allergies can be caused by seafood that you’ve eaten before with no issues, but once you develop a seafood allergy, you’ll usually have this allergy for the rest of your life.3
It can take some time for symptoms to occur after eating seafood. Most occur within minutes, but some people don’t experience symptoms until up to an hour after eating. As with other food allergies, the symptoms of a seafood allergy may range from mild to severe.
Seafood can be a hidden ingredient in many foods, which is why it’s important to read the label or ask before buying or eating certain foods. Ingredients in packaged foods can change at any time—and without warning. It is also important to avoid seafood restaurants, going to the fish market, and being in an area where seafood is being cooked.
Symptoms of a seafood allergy may include:
Shellfish fall into two different groups: crustaceans and mollusks. Some people with shellfish allergies are allergic to both types, but some may only be allergic to one.
Reactions to crustaceans tend to be particularly severe. Crustaceans cause the greatest number of allergic reactions. Many shellfish-allergic people can tolerate mollusks.
There are thousands of species of fish, but fish allergies are commonly related to:
A fish allergy is not as common as other food allergies, but it is important to take it just as seriously as the others because it can cause the same severe reactions. There is a high degree of cross-reactivity between different fish species, so healthcare professionals often advise their fish-allergic patients to avoid all fish.
You may be so used to avoiding fish or shellfish that you haven’t considered asking for help. So, how do you know if your symptoms are caused by a seafood allergy? If you think you or a loved one has a seafood allergy, don’t try to manage the problem on your own. A simple blood test can help your healthcare professional determine what could be causing your reactions. And knowing the true cause of your symptoms now may also help you avoid more serious issues in the future. For example, a food allergy reaction sends someone to the ER every 3 minutes. 4
Knowing if you’re allergic and what you’re allergic to can help you get relief.
1. Turner P, et al. Seafood allergy in children: a descriptive study. Ann Allergy Asthma Immunol. 2011; 106(6)494-501.
2. Sicherer SH, et al. Prevalence of seafood allergy in the United States determined by a random telephone survey. J Allergy Clin Immunol 2004;114:159-165.
3. Wood RA: The natural history of food allergy. Pediatrics. 2003, 111 (6 Pt 3): 1631-1637.
4. Clark S,et al. Frequency of US emergency department visits for food-related acute allergic reactions. J Allergy Clin Immunol. 2011; 127(3):682-683.