Dr. Tim Says...

Chicken skin: to eat, or not to eat 06/19/17
Change is here 06/12/17
Medical technology 03/27/17
The science behind the DASH diet, an overview: Part Two 08/01/16
The science behind the DASH diet, an overview: Part One 07/25/16
How the Standard American Diet (SAD) affects the brain (Part Two) 05/26/16
How the Standard American Diet (SAD) affects the brain 05/23/16
All "Dr. Tim Says..." Columns

Chef Tim Says...

Deviled Eggs 04/24/17
Roasting Fruit 04/03/17
Papadum 03/20/17
Capers make it better 02/06/17
Mustards: The Christmas Basket Challenge, Part 5 01/26/17
Canned Tuna from Spain: The Christmas Basket Challenge, Part 4 01/16/17
Ginger and Rice Noodles: The Christmas Basket Challenge, Part 3 01/12/17
All "Chef Tim Says..." Columns


 

Dr. Tim Says....



Shellfish Allergy

a plate of shrimp scampi

While peanut and egg allergy most often are found in children, shellfish allergy occurs mostly in adult patients. Although 1.9% of adults believe that they are allergic to shellfish, only about 1.3% of adults in the US actually have a physician-diagnosed shellfish allergy. The percentage of people with a shellfish allergy is fairly equal among age and racial or ethnic groups, but African-Americans are more likely to self-report an allergy. People who experience a severe reaction to shellfish may also experience reactions to fin fish as well, but just why that might be is not yet well understood. 

The major allergen in shellfish is the actin-binding protein tropomyosin. (Interestingly, parasites often associated with shellfish have also been found to be allergenic.) Crustaceans (shellfish) include crab, shrimp, krill, molluscs, and copepods. molluscs include clams, octopi, squid, and scallops. Copepods are small (1-2mm) crustaceans found in fresh water supplies all over the world and are used in the tap water supply to control mosquitoes and other insects. While the larger copepods are normally filtered out, the smaller ones can make their way into the water mains and are routinely found in the tap water of cities that rely on reservoir water, such as New York and San Francisco.1 

Those with shellfish allergies should be aware that beer and wine may be processed with clarification agents derived from fish bladder. Be cautious of them unless you know that either they have not been processed this way or that you are not allergic to fin fish as well as shellfish.

At one time there was a belief that the allergy to shellfish was caused by an allergy to iodine in the shellfish. The good news is that this myth began as a misinterpretation of studies done in the 1970s. We're not sure why shellfish became the focus of these studies, but in truth the results simply showed that 15% patients with any food allergies were also allergic to iodine based contrast.2

1. Muthiah, R., et al. Copepods: Worldwide Sources of Allergens - Partial Sequences of Three Unique Proteins. Journal of Allergy & Clinical Immunology 2005; 115(2): PS91.

2. Schabelman, E., and Witting, M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med. 2010; 39(5):701-7.

Timothy S. Harlan, M.D.
Dr. Gourmet