A new study published in the September issue of Allergy says that food allergies can be misdiagnosed through cross-reactions to common inhalant allergens in a way similar to how infectious diseases can be transmitted and misdiagnosed.
This does not necessarily mean "infectious" in the sense that those without allergies can catch them from others, but that food allergies can appear to be triggered (or possibly created via diagnosis) by existing allergies to airborne allergens.
How cross-reacting allergenic structures can work.
Immunoglobulin E (IgE), closely associated with allergic response, can be stimulated by a cross-reactive inhalant allergen which can in turn result in the appearance of allergic reactions to different foods. A scenario would go something like this: a person with a common allergy such as hay fever could be having reactions to that. Then, upon eating a food associated with allergy, such as peanuts, the reactions could result in the body seeming to have more severe reactions to peanuts. In diagnostic testing, the patient may appear to have a peanut (or other) allergy when in fact they have hay fever instead.
The researchers say that allergy testing should take into account clinically relevant sensitizations. Current testing, for example, would start with skin prick testing or IgE blood tests may be conducted to determine allergy. The difficulty is in the cross-contamination. A person may be reacting to an airborne allergen but the tests, geared towards consumptive allergens like peanuts or milk, could still show positive reactions. This would lead to a misdiagnosis of peanut or milk allergy.
In cases of unclear history, allergy needs to be confirmed by oral challenge tests, the researchers conclude.
"As we are facing an increasing incidence of pollen allergies, a shift in sensitization patterns and changes in nutritional habits, and the occurrence of new, so far unknown allergies due to cross-reactions are expected," the authors write.