Shellfish, Shellfish Everywhere, But Not a One to Eat
A steaming bowl of
bouillabaisse and a thick chunk of French bread might be just the thing to ward
off the winter blues. Or maybe it's a cup of hot, creamy chowder and a pile of
meaty scallops that drives the snow away. But not for you.
Even as you dip a small piece of roll into your friend's savory lobster stew, you're stopped by the famous words of Lucretius: "One man's food may be another man's poison."
Poisons often kill, and food allergies can, but rarely do. Hives or an itchy skin reaction, a scratchy throat, hoarseness, teary eyes, shortness of breath or swelling of mucous membranes in the mouth and throat are common symptoms of a food allergy. In rare cases, a sudden drop in blood pressure can signal anaphylaxis or shock which requires immediate medical attention.
"You can even get a reaction to shellfish if you haven't consumed any," says Leonard Bielory, MD, director of the division of allergy and immunology at UMDNJ-New Jersey Medical School. Simply touching the liquid in which the shellfish was cooked, or in some cases, inhaling the steam or cooking odors, can trigger symptoms.
According to Bielory, a shellfish allergy can occur within minutes or up to several hours later, and is actually an immune system reaction. The symptoms occur when the mast cells release histamine in response to their interaction with foreign protein molecules. It's not known why some people react to particular proteins and others do not.
The allergist says that some of these proteins are common to all shellfish; others are found only in one type. Researchers are beginning to analyze the chemistry of these proteins, Bielory says, but most of the allergens are not yet well-defined.
"So if you are allergic to one type of shellfish, such as crabs, assume you are allergic to shrimp, lobsters, crawfish and other shellfish, too," Bielory states. "The only way to safely handle the problem is to abstain."
For those who yearn for a Maine lobster claw dipped in butter, but have had an allergic reaction in the past, Bielory says taking an antihistamine before indulging will not work. "There is no prophylactic treatment that's effective," he says. He advises those who have had extreme reactions in the past to carry an epinephrine injector system Ð in case they inadvertently eat something that contains shellfish protein, such as fish stock, which may be used as a base in soups.
If you're dying to eat oysters, and have only had a reaction to shrimp in the past, you may want to contact an allergist for a diagnostic evaluation which can include skin tests or a blood test known as a RAST (radioallergosorbent test). Skin tests are more sensitive, especially in patients with a history of a systemic reaction. But in 74 percent of cases, the diagnosis is based on history alone, and patients are advised to keep away from all shellfish cooked and raw if they have reacted to even one kind.
For those whose reactions have been severe, it's particularly important to remember to read packaged food labels for seafood flavorings or unexpected sources of the allergen. You should also remember that any dish prepared in a seafood restaurant may be cross-contaminated with shellfish during handling or cooking.