Dear Dr. Andersen,
Thank you for your measured and well reasoned response to my Annals article last month. [See “A Letter In Response to ‘The Nuts in Our Schools’”]. My column was intended to be a little provocative in order to strongly counter the groundswell of public perception that food allergies represent a growing threat to kids in our schools. They simply don’t.
Several days after the Crozet Annals of Medicine went to press, the New York Times followed my lead with a front page article titled “Doubt Is Cast on Many Reports of Food Allergies.” The Wall Street Journal blog, the Los Angeles Times blog, and CNN all ran similar stories the same day. The source for the articles was not only the Crozet Annals of Medicine but also a landmark study published May 12, 2010 in the Journal of the American Medical Association. The study was a systematic review of the available evidence on the prevalence, diagnosis, management, and prevention of food allergies.
The authors reviewed 12,378 studies on food allergies published between 1988 and 2009.
That is a lot of studies. Only 72 studies ultimately were felt to be scientifically valid with the other 12,306 rejected due to poor methodology. Your observation that no studies are perfect is certainly true. Science is a messy business.
The authors concluded that food allergies affect more than 1% or 2% but less than 10% of the US population. Their closest estimate was around 3%.
Whether the prevalence of food allergies is increasing is not well established. The study you cite is I assume “US Prevalence of Self-reported Peanut, Tree Nut, and Sesame Allergy: 11-year follow-up.” in the May 2010 online Journal of Allergy and Clinical Immunology. I do not dispute that self-reporting of food allergies is increasing; in fact I satirically labeled it an epidemic in May’s column. This self-reporting does not square with the actual prevalence of food allergies as seen in several well done studies.
I will not presume to comment on your son’s specific medical condition; it sounds like he is in good hands medically and parentally.
The authors of the JAMA study do comment generally though, concluding that “A clinical consequence of our findings regarding lack of uniformity of criteria for diagnosis and the limited sensitivity and specificity of existing office-based tests for IgE sensitization is the potential for overdiagnosis of food allergy in the general population. Patients with nonspecific symptoms (rash, abdominal complaints) who have positive Skin Prick Test or serum food-specific IgE studies to foods have less than a 50% likelihood of actually having a food allergy (given the sensitivity, specificity, and prevalence).”
Other good studies noted that a positive skin test alone, especially to peanuts, without a positive food challenge of peanuts or any history of adverse reactions to peanuts was unlikely to represent a true food allergy.
Part of my purpose in writing my article was to counter the very frightening proposition that you lay out in your letter. “Finding out that only 1/1000th of a peanut can cause a severe reaction has made us incredibly nervous parents. When our son tells us his stomach hurts, instead of wondering if he’s got a virus, we immediately start wondering what he may have eaten and if we’re about to see something bad happen.”
Once again the JAMA authors have a general comment on this perception: “Inappropriately diagnosing such individuals with food allergy may unnecessarily subject them to broad dietary restrictions, the risk of nutritional problems from elimination diets (e.g., milk or egg elimination in children), significant anxiety and worry, and the social challenges food allergies cause.” Remember, these are allergy specialists’ conclusions after reviewing 12,000 studies.
Regarding your most important criticism, “I was disappointed in this article’s general suggestion that peanut allergies are not serious…”
The JAMA authors sort of support your position here. “The overdiagnosis or misdiagnosis of food allergy by medical practitioners obscures the substantial morbidity caused in patients truly affected by immune-mediated food allergy and serves to perpetuate some public misperceptions that food allergy is a trivial medical condition.”
If the tone of my article was not balanced by my statement that “Peanut allergies are very rare but are the most potentially lethal of all food allergies,” it is because the reality as measured is that fewer than one in 2 million kids with food allergies will die from them. There are statistically many much greater risks than microscopic food out there for kids with food allergies.
Many thanks for your careful reading of my article and your incisive comments. And as an afficionado of the punch line I particularly enjoyed yours. Touché!