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Don’t Ignore these Details about Living with a Shellfish Allergy

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Jessica was enjoying a plate full of crab legs. Suddenly, she felt dizzy, her stomach hurt, her lips swelled, and she developed a rash. She thought, “Could this be a shellfish allergy?”

She recovered from the incident, and days later, she met with a Board Certified Allergist.  Her doctor confirmed that she had in fact developed a shellfish allergy.

Remember: this post is for informational purposes only and may not be the best fit for you and your personal situation. It shall not be construed as medical advice. The information and education provided here is not intended or implied to supplement or replace professional medical treatment, advice, and/or diagnosis. Always check with your own physician or medical professional before trying or implementing any information read here. Keep in mind food production can change, always check food labels to be sure products are free of your particular food allergen. For further information please see full Disclaimer.

How Common is a Shellfish Allergy?

Shellfish allergies are fairly common and are one of the most common types of food allergies.  According to FARE (Food Allergy Research and Education), about 8 million Americans have a shellfish allergy.

Shellfish allergies may occur in childhood, but usually occur as an adult.

Someone with a shellfish allergy may be allergic to all shellfish, or may have an allergy to one or only a few specific types of shellfish.  Speak with your board certified allergist to find out what your specific allergy is.

Having a shellfish allergy does not mean that you have a fish allergy.  They usually don’t go hand in hand.  It is, however, possible to have an allergy to both.

A shellfish allergy can develop at any point in life, even if you used to safely eat shellfish in the past.

What are the 9 Most Common Food Allergies?

The top 9 food allergies also known as the big 9 allergens in the United States are:

  1. Milk
  2. Egg
  3. Peanut
  4. Soy
  5. Wheat
  6. Tree Nut
  7. Shellfish
  8. Fish
  9. Sesame
The Top 9 Food Allergens in the U.S. Top 9 Food Allergies. 1. Fish 2. Shellfish 3. Tree Nuts 4. Peanuts 5. Milk 6. Wheat 7. Egg 8. Soy 9. Sesame

You can be allergic to many other foods besides these top nine. 

What are Symptoms of a Shellfish Allergy?

Shellfish allergy symptoms can vary from person to person but some typical reactions are listed below.  Reactions may be mild (like having a stuffy nose and upset stomach) to severe.  Severe reactions may be life threatening.  

  • Hives
  • Swelling of lips, tongue, throat, face
  • Dizziness
  • Anaphylaxis
  • Itching or swelling of the lips, tongue, or throat
  • Diarrhea
  • Difficulty swallowing
  • Abdominal pain and cramps
  • Wheezing (difficulty breathing)
  • Nausea and vomiting
  • Runny nose
  • Congestion (stuffy nose)
  • Digestive problems
  • Coughing
  • Loss of consciousness

A shellfish allergy tends to be lifelong in most cases.

Types of Shellfish

There are many different types of shellfish.  Shellfish are usually referred to as either mollusks or crustaceans.

Crustaceans and Mollusks have different food labeling laws.  More on that later.


Crustaceans include prawns, crawfish, crabs, krill, langoustine, lobster, and shrimp.

Interestingly, crustaceans make up the majority of shellfish allergies.  It is much more common to be allergic to crustaceans rather than mollusks.

If you have a shellfish allergy, you may be able to eat mollusks, but not eat crustaceans and vice versa.


Mollusks include mussels, snails, clams, cockle, sea cucumber, octopus, squid, whelk, cuttlefish, abalone, oysters, limpet, sea urchin, periwinkle, and scallops.  As mentioned above, many individuals are allergic to specific shellfish, but some individuals are allergic to all shellfish.

Less Common Names for Foods to Avoid with a Shellfish Allergy

Avoid any foods that contain crustaceans or mollusks.

Less obvious names or less obvious possible food sources include but is not limited to:

  • Surimi
  • Fish stock or fish sauce which may be made from shellfish
  • Seafood flavoring
  • Glucosamine supplements
  • Bouillabaisse
  • Conch
  • Imitation Fish
  • Periwinkle, sea urchin (cockle)
  • Geoduck, cherrystone, littleneck, pismo, quahog (types of clams)
  • Lapas, opihi (types of limpet which is a mollusk)
  • Cuttlefish ink
  • Barnacles
  • Turban shell (whelk)
  • Calamari (squid)
  • Escargot (snails)
  • Crevette, scampi (may indicate shrimp)
  • Langoustine, scampi, coral, tomalley, moreton bay bugs, tomalley, and langouste (lobster) 
  • Crawdad, crayfish, ecrevisse (crawfish)  
Shellfish Allergy. Crustacean Allergy. Mollusk. Foods to avoid with a shellfish allergy (shrimp, crab, lobster, scallops, clams, mussels, octopus, etc)

Food Allergy Labeling.  About FALCPA

In 2004, the Food Allergen Labeling and Consumer Protection Act (FALCPA), identified the following foods as major food allergens:  milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soy.

Effective January 1, 2023, the FASTER Act  (the Food Allergy Safety, Treatment, Education, and Research Act) was signed into law, adding sesame as the 9th major food allergen recognized in the U.S. 

FALCPA  requires that foods or ingredients that contain major food allergens be labeled with the name of the allergen source.   

Labeling laws are different for crustaceans vs. mollusks.  Because crustacean allergies are more common, information about a crustacean shellfish allergy require listing on US food labels in plain language.  Listing the specific type of crustaceanon on the label is a requirement (example:  shrimp, crab).

The law does not require that mollusk ingredients be listed in plain language.

This difference in labeling of crustaceans vs. mollusks is very crucial to understand as many newly diagnosed individuals with shellfish allergies may not know that this is the case.  

FALCPA states that major food allergens be listed in one of three ways:

  1. In the ingredient list, using the allergen’s common name.  Example:  Ingredients:  Shrimp.
  2. By  citing the word “Contains” followed by the name of the major food allergen—for example, “Contains crustaceans shellfish (shrimp)”
  3. In the ingredient list in parentheses after a less common name of ingredient that may contain an allergen.  Example: Crevette (shrimp).

Made in a Facility/Cross Contamination Statements

Food manufacturers may use equipment to produce multiple products.  This may lead to cross contamination of allergens.  Some manufacturers disclose this information and others do not.  This is true for both FALCPA and non-FALCPA allergens.

Cross contamination statements are not a requirement in the U.S.  Call the manufacturer to learn about their manufacturing practices.

If you have a shellfish allergy and do not have a fish allergy, risk of cross contamination may be quite significant when dining at a restaurant that serves both fish and shellfish.  Ask how food is prepared at a restaraunts.

Shellfish Allergy Treatment

  1. Always read food labels and look for shellfish ingredients
  2. Avoid all foods related to your allergy.  Learn less common names for your particular food allergy.
  3. Become familiar with labeling laws.
  4. Talk to your Board Certified Allergist
  5. Be mindful of risk for cross contamination
  6. Know how to treat your shellfish allergy in the case of accidental ingestion.  Be sure to have not one, but two doses of epinephrine available when eating.  Talk to your doctor about how to treat symptoms of an allergic reaction and visit www.foodallergy.org for more detailed information about treating food allergies.

Final Thoughts

It is not uncommon to develop a shellfish allergy as an adult.  An allergy to fish does not mean an allergy to shellfish.  It is more common to have an allergy to crustaceans rather than mollusks.  

If you have a shellfish allergy, be sure to ask about how food is prepared when dining out.   

Always read food labels.

Carry two doses of epinephrine when consuming food in case of a serious allergic reaction.  

If you think you may be allergic to shellfish see a Board Certified Allergist.

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Last Updated on January 20, 2023 by Amber DeVore, RD, CSSD, CLT

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