Shell-Fish Free Diet

Shell-Fish Free Diet

September 01, 2015

Shellfish allergies are the most common allergy among adults in America, and they are more likely than most other allergies to manifest for the first time in adults. Shellfish allergies are allergies to two classes of foods: mollusks (which include clams, mussels, and oysters) and crustaceans (which include shrimp, lobster, and crabs). Although these two groups are fairly distant biological relatives, there is a high rate of allergic cross-reactivity between the two. So, many people who are allergic to any shellfish are advised to avoid all shellfish. Shrimp is the considered the most allergenic.


Different types of shellfish have high rates of cross-reactions with other types of shellfish, as noted above. The protein that most commonly causes shellfish allergies (tropomyosin) is also found in dust mites and cockroaches, and there is some evidence of cross-reactivity between shellfish and some insects.


The most common symptoms of shellfish allergy are hives (urticaria) and major redness and swelling below the skin (angioedema). Shellfish allergies are a major cause of anaphylactic shock.

Shellfish Allergies and Dietary Supplements:

Glucosamine, a dietary supplement sometimes recommended for patients with arthritis, is often made from the shells of crustaceans. The proteins that are most likely to cause food allergies are not found in the shell, and recent studies have indicated that glucosamine is safe for people with shellfish allergies; however, if you are concerned, you can try vegetarian glucosamine.

Another potential source of shellfish allergens is Omega-3 supplements, which are often made from seafood. The most common source used to manufacture these is fish (mostly cod liver), but check ingredients on the label before you take these.
Shellfish Allergies and Iodine:

Although certain shellfish are rich in iodine, there is no evidence that shellfish allergies raise the risk of an iodine allergy, nor that people with shellfish allergies need to take precautions to avoid iodine when undergoing medical tests. Iodine is not related to the protein that causes shellfish allergies.

Mollusks and Crustaceans:

Unless instructed otherwise by an allergist, people with shellfish allergies should avoid both mollusks and crustaceans because most shellfish allergies are caused by similar proteins. Some patients, though, can be determined through testing not to be allergic to one family and may eat that family safely.

People who are allergic to mollusks should avoid:

  • Clams
  • Oysters
  • Mussels
  • Abalone
  • Scallops
  • Cockles
  • Quahogs
  •  Squid (Calimari)
  •  Octopus
  •  Whelks
  •  Snails (Escargot)
  •  Limpets
  • People who are allergic to crustaceans should avoid:
  • Shrimp
  • Lobster
  • Crawfish (Crayfish or Crawdads)
  • Prawns
  • Crab
  • Langoustines
  • Sea Urchin

Shellfish and Labeling Laws:

Because shellfish are one of the eight most common allergens in the United States, they are covered by FALCPA (the FDA's Food Allergy Labeling and Consumer Protection Act). This requires that the presence of shellfish be listed on labels in clear English, either in bold type or following the list of ingredients after the word "Contains." However, FALCPA only refers to crustaceans, and not to mollusks. Shellfish is not a common hidden ingredient and doesn't generally lurk under unusual names in ingredient lists, so reading labels for shellfish is relatively simple.
Foods Containing Shellfish:

Shellfish are relatively easier to avoid in the diet than most of the other most common allergens. They are sometimes found in Worcestershire sauce, salad dressings, and other prepared sauces. Be aware that surimi (imitation shellfish) often contains shellfish extracts for flavoring and is often unsuitable for allergies, so check labels.

Shellfish Allergies and Anaphylactic Shock:

Beyond eating at restaurants, the greatest challenge in living with a shellfish allergy is likely the fact that shellfish allergies pose a greater risk of anaphylactic shock than many food allergies. In fact, shellfish allergies are responsible for more cases of anaphylaxis than any other food allergy. That's why people with shellfish allergies should speak with their allergist about their risk of anaphylaxis and know what to do in case of anaphylactic shock. If you are prescribed epinephrine, you should carry it on your person at all times.
Eating Out with Shellfish Allergies:

Shellfish abound in East Asian cuisine; eating at an Asian restaurant, whether Chinese, Thai, Japanese, Vietnamese, or Malaysian, is likely to be exceedingly tough with a shellfish allergy because of the place of shellfish in those cuisines and because of the high risk of cross-contamination.

If you do decide to eat East Asian food, be especially aware of condiments, which are among the most likely ingredients to include shellfish. Thai kapi and nam prik, Vietnamese mam tom, and Chinese dried shellfish are among the most common shellfish-derived condiments in these cuisines, but other sauces may include hidden shellfish. The two greatest risks in Japanese restaurants are cross-contamination at sushi bars and aerosolized seafood proteins and cross-contamination at hibachi-style (communal grill) restaurants. Seafood-only restaurants have a similarly high risk of cross-contamination, as many keep fish and shellfish in close proximity and cook these foods on the same grills.

Because seafood is fairly expensive, its presence is often indicated on restaurant menus, but never assume; always ask wait staff. Menu terms that imply a particularly high likelihood of shellfish include:

  • Bouillabase (a French fish soup)
  • Cioppino
  • A L'Americaine (a French sauce often served with lobster or other shellfish)
  • Crevette (the French term for shrimp)
  • Scampi
  • Ceviche (fish or shellfish "cooked" by marinating in an acidic citrus-based marinade)
  • Etouffée
  • Gumbo
  • Jambalaya

(information obtained from

Posted In:

Food Allergies Intolerances/Sensitivities