Topics in Allergy
Shellfish is a common food causing IgE allergic reactions (see Food Allergy handout). IgE types of food allergies cause immediate and potentially very severe life threatening reactions when even small amounts of the food are ingested. Managing this type of reaction requires awareness of sources of fish, having adrenalin (usually in the form of an EpiPen) available, and use of Medic Alert bracelets.
Shellfish are allergically unrelated to bony fish and allergy to shellfish does not mean you will be allergic to bony fish. Most people who are allergic to shellfish will react to many species of shellfish but some people react to only one species. Some people react to Crustaceans (shrimp, crab, lobster) but not to Mollusks (oyster, scallop, clam, squid). Some people will react if the shellfish is raw but not if well cooked. Some people do continue to eat species of shellfish they have eaten in the past without reaction but this is risky. Shellfish allergies can be quite severe and reactions have been seen after exposure to cooking odors from shellfish or from touching shellfish. Overall, if you are allergic to one shellfish, it is reasonably likely you may react to other shellfish and it is best to avoid all shellfish. Shellfish allergy has nothing at all to do with iodine and those allergic to shellfish to not have to worry about iodine. Many radiology (x ray) questionnaires ask about reactions to iodine and shellfish even though allergy to shellfish has nothing at all to do with reactions to x ray dyes.
Shellfish are relatively easy to avoid but be cautious in restaurants where shellfish may be cooked in the same cookware as other dishes. Make sure the dishes and pans have been washed with soap and water before your meal is prepared in them. In general it is best to avoid seafood restaurants even if you are not ordering seafood.
The FOOD ALLERGY NETWORK has additional and frequently updated information about reactions to shellfish and other foods.
Food Allergy Network
10400 Eaton Place, Suite 107
Fairfax, VA 22030-3179
703.691.3179 Fax 703.691.2713
You should carry an EpiPen and know how to use it. Caregivers also need to be instructed. Children can carry an EpiPen at school with a note from our office. EpiPens may be given through clothing. If the EpiPen is used, you need to be seen and observed in an emergency room. Reactions have recurred even 2-3 hours after the initial reaction seemed to be improving.
If you have an anaphylactic reaction to shellfish, spit the food out of your mouth, rinse and spit with water or other liquid, and use the EpiPen. USE THE EPIPEN AT THE EARLIEST SIGN OF A REACTION. You should also consider going to an emergency room unless the reaction was very mild. Even then there is a risk it could recur. Do not go to a restroom or other private place to use the EpiPen. Notify someone you are having an allergic reaction, tell them you are giving yourself a shot, and ask them to call 911. Wearing your Medic Alert bracelet is important and lets emergency personnel know what is happening if you are unable to communicate with them.
Patients at risk of anaphylaxis to foods or other materials should avoid beta blocker medications (used for heart, blood pressure, and glaucoma problems) as these will block the effect of the EpiPen.
With these precautions of avoidance, Medic Alert bracelet and availability of EpiPen shellfish allergy is a manageable problem. Although there have been rare exceptions fatal reactions almost never occur when an EpiPen is available and used early in the event of a reaction. New treatments for shellfish and similar food allergies may be available within the next few years.