Crustaceans, including crabs, lobster, crayfish, shrimp and prawn, commonly appear on dinner plates and in side dishes in many regions across the US and around the world. But for some, crustaceans can induce a severe allergic reaction. According to F.A.R.E, 1.2% of the US population have a shellfish allergy.
An allergy to one kind of crustacean is likely to induce reactions to others since there is extensive cross-reactivity. There is an additional risk of cross-reactions to insects like cockroaches, midges, and mites. Cross-reactions to molluscean species, brine shrimp, and fish parasites like the cod worm have also been observed.
What is the root cause of a shellfish allergy?
Crustaceans have one muscle protein in common: Tropomyosin. This protein has been identified in 21 crustacean species and is responsible for most of the allergic reactions.
Who is affected?
While shellfish allergy can appear in children, it is more likely to manifest in adults. Unlike some of the other Big 8 allergies, children don’t outgrow it, and reactions tend to worsen with each exposure. Approximately 60 percent of people with shellfish allergy experienced their first allergic reaction as adults. Shrimp, crab and lobster cause most shellfish allergies.
What foods can present a potential hazard?
Generally, cross reactivity is high for shellfish allergy. The likelihood that an individual will react to more than one, if not all, crustacean species is high. These include:
- Crawfish (crawdad, crayfish, ecrevisse)
- Lobster (langouste, langoustine, Moreton bay bugs, scampi, tomalley)
- Shrimp (crevette, scampi)
What are some unexpected foods where Crustaceans can be an ingredient?
Many products use Crustaceans as an ingredient, or are processed in a manner that presents a risk from cross contamination. Allergenic properties of Tropomyosin are not removed by heating and and can be dispersed in the atmosphere during processing. The following is a partial list of foods that can be a risk for shellfish allergy:
- Cuttlefish ink
- Fish stock
- Seafood flavoring (e.g., crab or clam extract)
- Fish sauce
Did you know?
- Shellfish fall into two different groups: Crustaceans (like shrimp, crab, or lobster) and mollusks (like clams, mussels, oysters, scallops, octopus, or squid). Some people with shellfish allergies are allergic to both groups, but some might be allergic only to one.
- Allergy to iodine, allergy to radiocontrast material (used in some radiographic procedures), and to crustaceans are not related.
- The widespread occurrence of Tropomyosin in other invertebrate species can cause Shellfish Allergic individuals to also react to non-dietary invertebrates (e.g. house dust mite, cockroach).
- The word Crustacean is the contemporary usage of the word Crustacea.
- The federal Food Allergen Labeling and Consumer Protection Act (FALCPA) requires that all packaged food products sold in the U.S. that contain shellfish as an ingredient must list the specific shellfish used on the label.
- Note! Unlike shellfish, mollusks are not considered major allergens under FALCPA. Manufacturers are not required to disclose their presence as an ingredient on a product label.
What are typical symptoms?
The symptoms of an allergic reaction to Crustaceans range from mild local reactions in the oral cavity to severe life threatening systemic reactions. More rarely are stomach symptoms. The most common reactions are:
- Stomach cramps or indigestion
- Hives all over the body
- Shortness of breath
- Wheezing or repetitive cough
- Tight, hoarse throat; trouble swallowing
- Swelling of the tongue and/or lips
- Weak pulse
- Pale or blue coloring of the skin
- Dizziness or confusion
AlerTox Sticks Crustacean
AlerTox Sticks kits are specially designed to help food manufacturers monitor levels of common allergenic proteins at every step of production and in a variety of matrices. As with all of our tests, the kits are easy to use, accurate, and robust.
AlerTox Sticks Crustacean detects the major allergens of Crustacean muscle – Tropomyosin (allergen Met e 1 of common shrimp, Art fr 5 of brine shrimp, Cra c 1 of North Sea shrimp and similar proteins of other species)
The test is applicable for qualitative detection of target antigens in the samples of complex foods and surface swabs. The sensitivity of the test may decrease in case of heat-processed food or fat-rich samples (e.g. in presence of oil or cream). Some fish processing technologies, eg preparation of surimi, selectively deplete the antigen (tropomyosin), sometimes resulting in weak positive or even false negatives.
Learn More About Shellfish Allergy
Shellfish Allergy on the American College of Allergy, Asthma and Immunology site
The Culprit Behind Shrimp Allergy on the NY Times