Eliciting doses established for objective allergic reactions in walnut allergy

Published online: January 18, 2017

In food allergy, determination of allergic reaction eliciting doses (EDs) of foods on a population level can provide the required scientific data to improve allergen risk management and precautionary (e.g. “may contain”) labeling strategies. Currently, precautionary labels are voluntarily applied to food products by industry without proper regulatory guidance. Data for a number of priority allergens have been established, but unfortunately, data to properly establish EDs in walnut allergy were lacking up until now.

Blankestijn and colleagues reported on a clinical eliciting dose study performed in adults with a suspected walnut allergy based on patient history in The Journal of Allergy and Clinical Immunology: In Practice. All eligible subjects were challenged with walnut in a double-blind, placebo-controlled food challenge (DBPCFC). For each allergic subject with objective symptoms, the highest cumulative amount of walnut protein that did not elicit an allergic reaction and the first dose where objective symptoms occurred were established. Three parametric models were used to plot the data and to establish the EDs. The EDs include the ED5, ED10, and ED50, the dose predicted to provoke an allergic reaction in 5%, 10%, and 50% of the walnut allergic population, respectively.

Objective symptoms occurred in 20 out of 33 positive food challenges (61%). The lowest dose that triggered objective symptoms was 0.31 mg of walnut protein. Based on the three models, the EDs ranged from 3.1 to 4.1 mg for the ED05, from 10.6 to 14.6 mg walnut protein for the ED10 and from 590 to 625 mg of walnut protein for the ED50. The ED05 values correspond to approximately 1/180 of a walnut kernel. Compared to EDs previously found for hazelnut allergy, walnut EDs are slightly higher, indicating that walnut allergic subjects are not more sensitive than hazelnut allergic subjects. For hazelnut allergy, a large amount of threshold data is available, making estimates based on these data reliable. Less data are available for other tree nuts.

When including the results from this study, the currently available data for walnut and cashew indicate that the ED values for hazelnut could be used as a conservative temporary placeholder when implementing risk management strategies for other tree nuts where little or no food challenge data are available.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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