Shellfish allergies are among the most common manifestation of food allergies, as well as some of the most dangerous. According to the National Institutes of Health, it is estimated that as much as 2.5 percent of the general population is allergic to some kind of shellfish or seafood. However, many misconceptions surrounding this disorder persist, and this confusion carries serious health consequences.
What causes shellfish allergy?
Like any food allergy, shellfish allergies are triggered by eating foods that either contain shellfish or were prepared alongside shellfish. The most common types of fish that trigger a reaction are also among the most commonly consumed species – shrimp is by far the most common cause of shellfish reactions as well as the most widely consumed, followed by crab, lobster, clam, oyster and mussels.
The allergen associated with most shellfish allergies is called tropomyosin, a protein that is found in animals with exoskeletons. However, there are several other possible allergens present in shellfish, including some that also occur in aquatic animals that normally grouped into the shellfish category. This is made more confusing with the fact that some fish may contain toxins that are poisonous to anyone, even non-allergic individuals, but closely resemble an allergic reaction.
Clearly there is a lot to clarify on the matter of seafood allergies. Fortunately, keeping an adverse reaction at bay is relatively straightforward.
Avoiding shellfish
The best course of action for those allergic to shellfish is to avoid consuming any food products containing them. Because it only takes a small amount of residue to trigger reactions in many people, it is often advised that allergic individuals avoid anything that could have been cross-contaminated with shellfish. In practice, this usually means avoiding seafood altogether.
Developing an allergy
In many cases, people suffer allergic reactions to certain foods as children but improve as they grow older. Unfortunately, the opposite is also true, as some people may develop a shellfish or seafood allergy in adulthood. While their allergy may only involve a specific species, experts at Food Allergy Research and Education caution against picking and choosing which types of seafood to eat.
Treating acute reactions
Upon eating food containing a seafood allergen, allergic individuals may experience a serious type of reaction called anaphylaxis. These reactions can occur within minutes, or may take up to two hours after ingesting the food. The most common signs of anaphylaxsis due to any food allergy are difficulty breathing and reduced blood pressure. These key symptoms often occur in conjunction with swelling of the skin, abdominal pain and several other problems.
An allergic reaction to shellfish could be fatal in some people with a large enough dose. Sufferers of these allergies are advised to carry an epinephrine injector. These devices inject a dose of epinephrine directly into the muscle tissue, usually on a leg or arm. This usually resolves allergic symptoms with time, but allergic individuals or anyone around them should call 911 after administering the shot.
Differential diagnosis
While shellfish allergies have been known to occur in adults who were previously not allergic, consumption of some kinds of seafood can result in a type of poisoning that may appear similar to an allergic reaction, but is much different. Shellfish poisoning most often occurs after consuming mussels, clams, oysters and scallops, and is unrelated to poisoning caused by improper preparation. The most common forms of shellfish poisoning manifest as gastrointestinal issues including nausea and vomiting, but are generally not life-threatening and resolve within a day. Any cases that last longer or result in very severe symptoms require medical attention.
