Threshold Dose Distribution in Walnut Allergy

Background: In food allergy, eliciting doses (EDs) of foods on a population level can improve risk management and labeling strategies for the food industry and regulatory authorities. Previously, data available for walnut were unsuitable to determine EDs.

Objective: The objective of this study was to determine EDs for walnut allergic adults and to compare with previously established threshold data for peanut and tree nuts.

Methods: Prospectively, adult subjects with a suspected walnut allergy underwent a low-dose double-blind, placebo-controlled food challenge. Individual no observed and lowest observed adverse effect levels were determined and log-normal, log-logistic, and Weibull models were fit to the data. Estimated ED values were calculated for the ED_5, ED₁₀, and ED₅₀, the dose respectively predicted to provoke an allergic reaction in 5%, 10%, and 50% of the walnut allergic population.

Results: Fifty-seven subjects were challenged and 33 subjects were confirmed to be walnut allergic. Objective symptoms occurred in 20 of the positive challenges (61%). The cumulative EDs in the distribution models 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.

Conclusions: Our data indicate that population EDs for walnut are slightly higher compared with those for peanut and hazelnut allergy. Currently available data 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.