Almost seven million Americans have an allergy to shellfish based on consumption amount, age, and locale.

Shellfish are aquatic animals with a shell or shell-like exoskeleton. The two major species are crustacea and mollusks (American College of Allergy, Asthma, and Immunology, 2024). One of the top nine most common food allergies, the usual onset is in adulthood, but shellfish allergy can also impact up to 0.5 percent of children. Shellfish allergy symptoms can differ broadly, but reactions are typically more severe than with most other food allergens, as anaphylaxis is a common result (Woo & Bahna, 2011.) Unfortunately, a shellfish allergy is typically lifelong (Uptown Allergy & Asthma, 2024).

Shellfish allergy is an immunoglobulin E (IgE) mediated allergy, meaning that after eating, handling, or breathing in shellfish, the body’s immune system overreacts by “producing IgE antibodies which bind to mast cells . . . .[After] the shellfish protein allergen binds to the IgE antibody on the mast cell, the mast cell will release histamines that trigger allergy symptoms” (Uptown Allergy & Asthma, 2024). The body can react with any or numerous symptoms, such as (American College of Allergy, Asthma, and Immunology, 2024; Cleveland Clinic, 2023; Hirsch, 2024):

• Tightness in throat, hoarse voice
• Pale or blue coloring of the skin
• Hives or red spots on the skin, itching
• Contusion
• Worsening of eczema
• Tingling or swelling of the lips, tongue, or throat
• Chest tightness, wheezing, coughing, shortness of breath, and difficulty breathing
• Stomach issues, including pain, cramps, nausea, indigestion, vomiting, or diarrhea
• Dizziness, weak pulse
• Anaphylaxis, a severe, potentially fatal allergic reaction often involving several parts of the body
• Itchy, watery, or swollen eyes
• A drop in blood pressure causing lightheadedness or fainting

Shellfish Allergy Causation

Most individuals with a shellfish allergy are only allergic to crustacean species, such as lobster, crawfish, and shrimp. It is possible to react to one kind of shellfish but eat another type without an issue. However, approximately 14 percent of those with a shellfish allergy are allergic to both crustaceans and mollusks (Alonso et al., 2022). Due to the potential for a life-threatening reaction experts suggest that those allergic to any shellfish avoid all varieties.

Tropomyosin, a muscle protein, is the prominent allergen in shellfish and causes cross-reactivity among types of shellfish species, especially within crustaceans. (Woo & Bahna, 2011).

There is a common misconception that iodine provokes an allergic reaction to shellfish. Because iodine is not a cause for shellfish allergy, there should be no concern about any cross-reactions with iodine or iodine-containing radiocontrast material used in MRIs and other medical procedures (Cleveland Clinic, 2023).

Preparing for Shellfish Allergies

If you are working in the camp kitchen or dining hall this summer, know that tiny particles of shellfish protein can be emitted via vapors, causing a possible potent reaction in those who are very sensitive. Because of this ominous threat, you should be aware of all ingredients within each menu offering (American College of Allergy, Asthma, and Immunology, 2024).

Be aware, too, that the federal government does not require manufacturers to list mollusk shellfish ingredients on their labels, because they (clams, mussels, oysters, or scallops) are not classified as a major food allergen. If a label states the food item contains shellfish, this means crustacean shellfish. For the camper who has a rare allergy to mollusks, it may be necessary to contact food product companies to ask about mollusk ingredients or cross contamination.

Your camp may consider abstaining from serving shellfish to greatly reduce risk. 

Imperatives for Campers with Shellfish Allergy

Make sure you know where the prescription epinephrine auto-injectors (EpiPens) are kept. These should always be near your campers with a shellfish allergy for easy access and fast access. If you don’t know how to administer an EpiPen, ask your camp leader if they can organize a training session by your camp’s medical staff, so you’ll be prepared in the event of an emergency.

Every second counts in an allergic reaction. If a camper begins to have serious allergic reactions such as swelling of the mouth/throat or breathing difficulties, the EpiPen should be administered immediately. An EpiPen should also be used if the camper begins having symptoms in two different areas of the body, such as vomiting and hives. Then call 911 and get the camper to an emergency room, because there is a possibility of more reactions (Hirsch, 2024).

Shellfish Poisoning

Shellfish poisoning often guises as an allergic reaction. The five types of shellfish poisoning are:

1. Paralytic is the most common and severe shellfish poisoning. Initial manifestations are neurological, including numbness and tingling or burning of lips, tongue, and throat, which can extend to other areas of the body. The extremities then experience muscular weakness, and onset of paralysis may happen within two to 12 hours.
2. Neurotoxic shellfish poisoning displays both gastrointestinal and neurologic symptoms. Symptoms are numbness of lips, tongue, and throat, spreading to other areas of the body. Muscular aches, vertigo, and reversal of hot and cold temperature sensation ensue along with nausea, vomiting, abdominal pain, and diarrhea.
3. Amnesic shellfish poisoning — primarily presents as vomiting, diarrhea, and abdominal cramping. Sometimes neurological dysfunction can occur, including confusion, disorientation, and short-term memory loss. Coma and seizures may also occur.
4. Diarrhetic is the mildest toxic shellfish poisoning, which typically causes gastrointestinal dysfunction including diarrhea, nausea, vomiting, abdominal pain, and cramps. Roughly 10 percent of patients experience chills, fever, or headache.
5. Azaspiracids (AZA) shellfish poisoning causes extreme gastrointestinal human intoxications. Cases have been confirmed in Europe, Africa, and Canada. Tested on mice, AZA has induced widespread organ damage, proving to be a potent toxin.

Bacterial and Viral Reactions to Shellfish

Bacterial toxins and bacterial and viral infections can also masquerade as a shellfish allergy. The three common culprits are:

• Vibrio vulnificus. Although rare, this is the leading cause of seafood consumption death in the United States and has been reported to stem from a variety of seafood, including shrimp, fish, oysters, and clams. Consuming undercooked or raw seafood (primarily raw oysters) contaminated with V. vulnificus can result in severe blood poisoning.
• Clostridium botulinum. Foodborne botulism is caused by eating shellfish contaminated by preformed toxin. Symptoms include nausea, vomiting and diarrhea, dry mouth, and double or blurred vision. Paralysis may occur and cause respiratory failure.
• Staphylococcal aureus. This enterotoxin grows in contaminated food — in this case shellfish — that has been left sitting out at room temperature too long. The quick onset of symptoms are nausea, vomiting, abdominal cramps, and diarrhea (Woo & Bahna, 2011).

Campers or fellow staff exhibiting any of the preceding symptoms should be evaluated by camp medical personnel and taken to the emergency room, if needed.

The Outlier of the Top Nine Allergens

Fortunately, shellfish is not a base ingredient, like wheat-derived flour, nor an emulsifier, such as egg or milk. Soy is a binding ingredient, and peanuts and tree nuts surround us almost daily in candies, baked goods, and nut butters. Unlike fish, which are found in American rivers, lakes, and coastal waters, shellfish is overwhelming coastal fare, with a smaller percentage found in the bayous and creeks of deep southern states. Still, wherever you are at camp this summer, the following is a list of foods that should be avoided to keep your campers and fellow staff safe.

Shellfish Allergy Avoidance List

• Barnacle
• Cocktail shrimp
• Crab (Crab cakes, crab dip)
• Crawfish/crayfish (crawfish boil, crawdad, ecrevisse)
• Creole or Cajun gumbo
• Jambalaya
• Krill and krill oil
• Lobster (langouste, langoustine, Moreton Bay bugs, Scampi, Tomalley)
• Lobster bisque, lobster roll
• Prawns
• Scampi
• Shrimp (crevette, shrimp chips, scampi)
• Sea urchin
• Sushi
• Tomalley

Your doctor may advise you to avoid mollusks or these ingredients:

• Abalone
• Calamari
• Clams (cherrystone, geoduck, littleneck, pismo, quahog)
• Clam chowder, clam juice
• Cockle
• Conch
• Cuttlefish
• Escargot
• Limpet, lapa, opihi
• Mollusks
• Mussels
• Octopus
• Oysters (all varieties)
• Oyster sauce (used in some Asian cuisine)
• Periwinkle
• Scallops
• Sea cucumber
• Sea urchin
• Seafood flavoring (crab or clam extract)
• Snails (escargot)
• Squid (calamari)
• Squid ink pasta
• Whelk (turban shell)

Shellfish are often found in the following:

• Bouillabaisse (a French fish soup)
• Ceviche (fish or shellfish in an acidic citrus marinade)
• Cioppino (fish stew)
• Clamato (a clam broth and tomato juice mixture sometimes used in Bloody Mary drinks)
• Crevette (the French term for shrimp)
• Cuttlefish ink
• Etouffee (Cajun crawfish or shrimp dish)
• Fish stock or fish sauce (sometimes made from krill)
• Glucosamine supplements
• Gumbo (fish and shellfish stew)
• Imitation crab (usually contains up to 2 percent king crab meat, plus artificial and natural crab and lobster extracts)
• Imitation fish
• Jambalaya (Cajun rice dish often made with shrimp or crawfish)
• Mam tom (Vietnamese fish sauce)
• Marine collagen supplements (check labels for skin or muscle of shellfish)
• Nam prik (Thai fish sauce)
• Paella (Spanish rice dish usually made with shrimp)
• Scampi (contains lobster or shrimp)
• Seafood flavoring (e.g., crab or clam extract)
• Seafood stews
• Surimi (fake crab)

Nonfood shellfish sources:

Camps may use any of the following products in animal programs, landscaping, or your health-care center:

• Compost or fertilizers
• Fish food
• Pet food
• HemCon bandages (a wound dressing derived of shrimp shells)
• Calcium supplements made from oyster shells or coral
• Glucosamine
• Omega-3 supplements (often made from fish, but occasionally made from shellfish)

References

• American College of Allergy, Asthma, and Immunology. (2024). Shellfish. ACAAI. acaai.org/allergies/allergic-conditions/food/shellfish/
• Alonso, L. L., Armstrong, L., & Warrington, S. J. (2022, September 26). Shellfish allergy. Treasure Island, FL: StatPearls Publishing.
• Bradley, J. (2023, December 1). Foods to avoid when you have a shellfish allergy. VeryWell Health. verywellhealth.com/shellfish-allergy-diet-foods-to-avoid-1324478#toc-recipes-that-contain-shellfish
• Cleveland Clinic. (2023, November 1). Allergies: Shellfish. my.clevelandclinic.org/health/diseases/11319-allergies-shellfish
• Hirsch, L. (editor). (2024). Shellfish allergy. Nemours KidsHealth. kidshealth.org/en/parents/shellfish-allergy.html
• Uptown Allergy & Asthma. 2024. Shellfish allergy symptoms, causes, and when to see a doctor in New Orleans, LA. uptownallergyasthma.com
• Woo, C. K., & Bahna, S. L. (2011). Not all shellfish “allergy” is allergy! Clinical and translational allergy, 1(1), 3. doi.org/10.1186/2045-7022-1-3

Kimberly Whiteside Truitt is a former food service manager at Camp Gilmont and Camp Zephyr and has served on Camping Magazine’s Editorial Advisory Committee. Kimberly was a presenter at the 2018, 2020, and 2023 North American Food Service and Maintenance Conferences.