Slate reports that the numbers of people suffering from shellfish and other food allergies may be significantly overstated. The article traces the source of confusion to a 2004 paper in the Journal of Allergy and Clinical Immunology that misrepresents the percentage of the population with seafood allergies. For one thing, the authors of the paper were non-statisticians trying to perform statistical work. For another, the survey questions were biased.
If you want to influence the answers in a survey, how you ask a question matters as much as what you ask. In the seafood study, pollsters dialed random numbers and asked whether any household members were allergic to seafood. This kind of phrasing yields a far greater number of “yes” responses than the question “has a medical professional diagnosed you with a seafood allergy?” Criteria for “convincing self-report” in the study were highly subjective, bumping up the numbers a bit more.
Throw in pharmaceutical companies selling allergy meds, a complicit media eager for scary stories, and eagerly gulled consumers and you’ve got a classic health myth.
Nuts to That: The people profiting from food allergies [Slate] (Thanks to Joanne!)