Shellfish Allergy: A Complete Guide

If you or loved one is struggling to manage a severe seafood allergy, you are not alone! While one can technically be allergic to anything, there are nine major food allergens that are . Shellfish of the top nine major allergens known to cause the most allergic reactions and affects nearly 7 million Americans.

Read our guide to learn how to manage and overcome your shellfish allergies!

What Is A Shellfish Allergy?

A food allergy occurs when the body mistakenly identifies an otherwise harmless substance as dangerous. The immune system creates IGE antibodies meant to attack and fight off this “harmful” substance which can cause an array of symptoms ranging from mild to life threatening. 

If someone is allergic to shellfish, that means that their body reacts to the protein found in the various forms of shellfish. A Shellfish allergy should be taken seriously as it can cause anaphylaxis, a life threatening reaction that requires epinephrine.

Risk Factors

Who’s more likely to develop a shellfish allergy? There is actually no definitive answer to this because food allergies are very individualized conditions. Almost anyone could develop an allergy, even if you were able to consume shellfish before without any adverse reactions.

While a shellfish allergy can develop at any stage of life, 60% of those with shellfish allergy don’t develop symptoms until adulthood. Shellfish allergies impact up to 2.3 percent of the population in the United States, making it among the most common food allergies.

You are far more likely to develop a shellfish allergy in your lifetime if you have family members that struggles with food allergies of any kind. If you live with conditions such as asthma, this can also put you at greater risk of anaphylaxis when allergic to shellfish.

Types Of Shellfish

The term Shellfish refers to both mollusks and crustaceans. Sometimes these sea creatures are referred to as the “bugs of the sea.” Many mollusks such as clams, mussels, oysters, scallops, have hinged two part shells and are classified as “Bivalves”. However, octopus, sea snail, and squid are also considered to be mollusks despite their lack of shell and can still cause reactions.

Crustaceans on the other hand have jointed legs, hard shells, and no backbone. Crab, crayfish, lobster, prawns and shrimp are all examples of crustaceans.

It is possible to be tolerant of some types of shellfish and allergic to others. According to one study, about 14% of individuals are allergic  to both forms of shellfish. If you have a history of a shellfish allergy and are unsure which types of shellfish you are allergic, proceed with caution and see an allergist to be tested for both types. 

If you have a shellfish allergy, you will want to avoid the following (unless otherwise stated by an allergist):

  • Abalone
  • Clams (such as cherrystone, littleneck, pismo, quahog)
  • Cockle
  • Conch
  • Crab
  • Crawfish and crayfish
  • Lobster
  • Mollusks
  • Mussels
  • Octopus
  • Oysters
  • Scallops
  • Shrimp and prawns.
  • Snails
  • Squid (calamari).

Shellfish and finned fish are not the same type of animal. While they are both creatures of the sea, it is possible to tolerate eating finned fish while having a shellfish allergy and vice versa.

Please note that the potential for cross contamination between the two may be relatively high as fish and shellfish are often prepared in similar areas.

Anaphylaxis and Shellfish Allergy

Anaphylaxis is a severe and life threatening type of allergic reaction. Those with a food allergies should always carry two epinephrine autoinjectors with them at all times. Epinephrine can stop an anaphylactic reaction and save a life if used quickly enough. Anaphylaxis is a medical emergency and should be taken seriously.

Anaphylaxis is a multisystem reaction. Look out for two or more system reactions or a large drop of blood pressure when evaluating an allergic reaction. An anaphylactic reaction would include two or more of the following:

  • Trouble breathing or wheezing
  • Itchy or red skin
  • Hives or rashes 
  • Itchy or swollen throat, nose, or eyes
  • Swelling in the lips or face
  • Stomach pain, diarrhea, or vomiting  
  • Feeling faint, dizzy or confused
  • Feeling a sense of doom

While anti-histamines may help relieve mild reactions, epinephrine is the only effective treatment for anaphylaxis. Always call 911 and administer epinephrine right away if you suspect an anaphylactic reaction.

Airborne Reactions

Airborne reactions to allergens are rare, but certainly not impossible. There are several documented cases of seafood airborne reactions occurring. Seafood is known to release protein when exposed to high temperatures, so those with shellfish allergies may experience symptoms when near shellfish that is steamed, boiled, or fried.

Those with asthma and shellfish allergy are more likely to experience symptoms when exposed to shellfish that is cooking. To be safe, avoiding kitchens, restaurants, and enclosed markets where shellfish is cooked is a good idea.

Cross Contamination

Even trace amounts of allergens invisible to the naked eye are enough to trigger a reaction in some individuals with severe allergies. That’s why it’s very important to read food labels and have an understanding of how certain food items are prepared. If someone were to cook shellfish in a pot and then use that pot without cleaning it to cook a safe, non-shellfish meal, for example, that meal now has traces of shellfish and may cause a reaction. You can avoid cross contamination by cleaning surfaces and cooking ware and utensils well or by using separate cooking ware and utensils all together.

Insect Cross-Reactivity

While eating insects in the US is not as popular as some places around the world, the practice is seen as a good source of protein and more environmentally friendly. It’s reported that  2,000 species are eaten by more than 2 billion people worldwide. However, for those with a Shellfish allergy, eating insects may not be a good idea due to cross-reactivity between insects and shellfish. Cross-reactivity occurs when the body confuses proteins from its allergenic source with another source that has a very similar protein structure. 

According to one report, most shellfish allergic individuals react to a protein called tropomyosin, which is also commonly found in insects. Humans actually have this protein in their bodies too, and we use it to contract our muscles and move.

While tropomyosin is found in several types of animals, the make up of the tropomyosin is different between shellfish and most other types of animals. However, there are high tropomyosin similarities between shellfish and insects like crickets, fruit flies, grasshoppers, cockroaches, locusts, and dust mites. So the risk of cross reactivity between shellfish and these insects is high.

Common Sources of Shellfish

Shellfish like crab or lobster can star as the main component of a dish, but sometimes Shellfish is not always as obviously placed. It is important to always read ingredient labels to make sure that the food you are eating is shellfish free. The FDA requires all shellfish to be clearly labeled on ingredient labels under the 2004 Food Allergen Labeling and Consumer Protection Act. Some common places you may find shellfish include:

  • Seafood flavoring
  • Surimi
  • Fish sauce/ fish stock
  • Bouillabaisse
  • Cuttlefish ink
  • Glucosamine

Enjoy A Life Free From Shellfish Allergies

The good news is shellfish allergies can be overcome! Through our Tolerance Induction Program™ (TIP), we treat all Top 9 major food allergens including, shellfish. By the end of the program, patients can achieve food freedom and successfully eat as much shellfish as they want, without restriction, or fear of reaction!

Schedule your free consultation with one of our program specialist and look forward to a better tomorrow!