Food allergies can be difficult to understand and manage. I speak from experience. Our son is allergic to eggs, peanuts and cashews. At my house, all food labels must be read, and care must be taken when going out to eat.
As a fisheries scientist, luckily I’m not allergic to finfish or shellfish — but, unfortunately, I know people who are, even other fisheries scientists.
So, it was no surprise when I read that shellfish cause one of the most common food allergies worldwide — and the third most common in U.S. children. The Mayo Clinic defines a shellfish allergy as “an abnormal response by the body’s immune system to proteins in certain marine crustaceans and mollusks, such as shrimp, crab, lobster, squid, oysters, scallops and others.”
Is the prevalence of this food allergy changing over time? Does it affect some groups of people more than others? Can you get a shellfish allergy later in life? The answers to these questions can raise awareness and spur further research to understand this important public health issue.
From October 2015 to September 2016, researchers surveyed a nationally representative sample of 40,443 U.S. adults to determine the prevalence, distribution, and severity of allergies, including shellfish. The investigative team considered this allergy to be present when respondents reported having experienced at least one severe condition, such as hives, swelling, difficulty swallowing, throat tightening, wheezing, vomiting, chest pain, rapid heart rate, etc.
Self-reported responses revealed that 2.9% of U.S. adults have a shellfish allergy, up from 2.6% in 2002. Women are more likely to have shellfish allergy than men. Whites were less likely to have a shellfish allergy.
Interestingly, residents living in ocean-adjacent counties had a greater chance of having a shellfish allergy compared to those living in a non-coastal county. However, those living in ocean-adjacent counties were less likely to experience severe reactions.
While nearly half (45%) of adults with a shellfish allergy reported visiting the emergency room for a reaction at least once in their lifetime, a similar amount (40%) only encountered mild or moderate reactions.
Half of the adults reported developing a shellfish allergy during adulthood. Nearly 1 in 5 adults with a shellfish allergy also had a finfish allergy.
Anyone with a suspected shellfish allergy should consider testing and counseling about how to avoid allergenic foods.
C.M. Warren et al. 2019. Prevalence and characteristics of adult shellfish allergy in the United States. J. Allergy Clin. Immunol. Vol. 144. No. 5, pp. 1435-1438.e5.
Summary compiled by Scott Baker
Lead photo from the NCSG photo archives
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