Shellfish is a term used by cooks which includes crustaceans such as shrimps, crawfish, crabs, lobster, langoustines, and mollusks such as clam, mussels oysters, scallops, and sea urchins.
Shellfish allergy is one of the most common food allergies in the United States, affecting about 2% of the adult population. It is not very common in children. In the United States, the highest rate of shellfish allergy occurs in African American adults. Overall, shellfish allergy accounts for up to 1/3 of all serious allergic reactions. Shellfish allergy is usually lifelong- it rarely goes away.
Different people will have different sensitivities to shellfish, so that some may react to trace amounts found in the air from the food being cooked, while others won’t have a reaction until a few bite size pieces have been swallowed.
Typically, individuals allergic to 1 type of shellfish have a very high chance (75%) of becoming allergic to other shellfish. It is thus very important to avoid all shellfish types, not just the one or two that you might initially have had a problem with.
There is little, if any, cross-reactivity between fish and shellfish. Studies demonstrate that only about 10% of people allergic to shellfish will also have a problem with fish (and vice versa). Caution must be taken when eating fish however, as shellfish is often processed on the same equipment used to process fish, leading to possible contamination of the fish with shellfish particles.
Are Shellfish Allergic Individuals Allergic to Iodine?
This is a common misconception. The idea that shellfish allergic patients could have problems with iodine appears to have started in the 1970’s and has been widely disseminated ever since. However, there is no evidence that this is true. There is no relationship between shellfish, iodine, and radio contrast dyes.
Avoiding shellfish may appear easy at first glance, but accidental exposures occur frequently. It is not uncommon for people to have reactions in restaurants where the person had their meal prepared in a pan that was previously used to cook some type of shellfish. It is thus important to request that your meal be prepared on cookware that has been cleaned so that there are no
residual amounts of shellfish from a previous meal in your food. It is also important to read labels carefully, as shellfish can sometimes be added as a flavoring in foods you might not otherwise be expected to contain this type of food. Reading labels of over the counter products, including “natural” remedies and herbal supplements is also important. For example, some weight loss
products contain small amounts of a shellfish derivative called Chitosan. Glucosamine, commonly used in over the counter products for osteoarthritis, can also be derived from the shells of crabs and lobsters. While there is no conclusive evidence that Chitosan and Glucosamine are harmful in patients who are allergic to shellfish, it is best to avoid these products until further discussion with your allergist who can do some tests to ensure they are safe for you to ingest.
Avoid foods that contain:
Foods which may contain shellfish: