Only Half of Suspected Food Allergies Real

A fascinating and unusually readable article on food allergies was recently published in the German journal Deutsches Ärzteblatt International. "Food Allergy in Adults: An Over- or Underrated Problem?" by C. S. Seitz, P. Pfeuffer, P. Raith, E. Bröcker, and A. Trautmann, Dtsch Arztebl Int 2008; 105(42): 715-23
DOI: 10.3238/arztebl.2008.0715.

An English translation of the article can be found on the journal's website.

They tested 419 patients sent to a clinic because their symptoms indicated a food allergy. However, after extensive testing, only 214 tested positive for an IgE-mediated true allergy.

Background:
10% to 20% of the population sees itself as suffering from food allergy, yet genuine, immune-mediated food allergy is suspected by patients and their physicians far more often than it is actually shown to be present. The unfounded suspicion of an IgE-mediated food allergy can substantially impair a patient's quality of life through needless dietary restriction and the accompanying anxiety. On the other hand, an IgE-mediated food allergy that has gone undiagnosed or that has not been taken seriously can manifest suddenly with anaphylaxis, which may be life-threatening. The present study, carried out on a large cohort of patients, underscores the importance of differentiating IgE-mediated food allergy from other, non-allergic types of food reaction.

Methods:
419 patients that had been referred to our outpatient allergy clinic for suspected food allergies underwent a standardized allergologic diagnostic evaluation, including thorough allergologic history-taking, IgE serology, and challenge tests when indicated.

Results:
214 patients (51.1%) were found to have an IgE-mediated food allergy. Almost half of these patients (24.3% of the overall group) had previously experienced food-induced anaphylaxis. In 205 patients (48.9%), however, an IgE-mediated food allergy was ruled out as far as possible.

Conclusion:
Only a comprehensive allergologic evaluation performed by an experienced allergologist in accordance with current guidelines can protect patients from the negative consequences of excessive concern about a non-existent food allergy (e.g., needless dietary restriction) or, on the other hand, the negative consequences of inadequate attention to a genuine food allergy (anaphylaxis). A proper evaluation consists of detailed allergologic history-taking, skin tests, and challenge tests when indicated.

Other interesting findings not included in the abstract were that a full 97.6% of symptoms manifested within four (4) hours and that positive skin-prick tests had little predictive ability, but negative ones did.