Likelihood of Immediate Food Challenge Reactions Varies by Age, History, Allergens, and Levels of Sensitization

The diagnosis of food allergy is challenging due to different immunologic mechanisms and diversity of symptoms. An open or double-blinded oral food challenge (OFC) was performed on 391 children (aged 0.2-16.9 years) with suspected cow's milk (n = 266) or wheat allergy (n = 125) to characterize immediate, delayed, and transient symptoms, and to evaluate the role of earlier food-related symptoms and immunoglobulin E (IgE)-[pmediated sensitization for the OFC outcome. The OFC resulted in an immediate positive reaction in 38% (n = 148) and a delayed positive reaction in 21% (n = 81) of the 391 children. Transient reactions, the majority of which were localized skin reactions, were seen in almost third (n = 50) of the patients with a negative OFC result (n = 162/391). Immediate localized skin reactions were more common during the milk challenge (p = 0.010), whereas immediate lower respiratory tract symptoms (p = 0.001) were more common during the wheat challenge. Although 14% (n = 21) of those with an immediate reaction received i.m. adrenalin as a treatment of the reaction, there were no life-threatening events. Multivariate analyses revealed that independent risk factors for the immediate OFC outcome were earlier moderate-to-severe immediate food-related reactions, marked IgE-mediated sensitization to the suspected food, and in case of wheat, age <12 months. The accuracy of OFCs can be enhanced without increasing the risk of serious allergic reactions by taking into account earlier food-related symptoms and the level of IgE-mediated sensitization, by refining our knowledge of transient nonspecific reactions, and by applying standardized OFC protocols with over-one-day challenges.