How much walnut does it take to provoke an allergic reaction?

Knowing the eliciting dose on a population level – that is, the amount of allergen required to provoke an allergic reaction in most sensitised people – helps the food industry and regulatory authorities manage food allergen risks in the supply chain, and inform risk management and labelling strategies.

Concerted efforts in recent years have seen greater knowledge of the eliciting dose of most of the major food allergens, however until now, the eliciting dose of walnut has not been established.

A recent study carried out by researchers in the Netherlands and the Food Allergy Research & Resource Program (FARRP), University of Nebraska, USA, challenged 57 adult walnut-allergic participants in a low-dose double-blind, placebo-controlled trial. Thirty-three of the subjects were confirmed to be walnut allergic through this challenge and individual ‘no observed’ and ‘lowest observed’ adverse effect levels were determined.

The population eliciting doses ranged from 3.1 to 4.1 mg for the ED05 (where 5% of the allergic population reacted), from 10.6 to 14.6 mg walnut protein for the ED10, and from 590 to 625 mg of walnut protein for the ED50 (where 50% of the allergic population reacted).

The authors (who include Dr Geert Houben, TNO and Dr Joe Baumert and Dr Steve Taylor, FARRP from the VITAL Scientific Expert Panel) suggest their data indicate that population eliciting doses for walnut are slightly higher compared with those for peanut and hazelnut allergy but that the eliciting dose 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.

Reference: Blankestijn et al. 2017 Journal of Allergy and Clinical Immunology in Practice. pii: S2213-2198(16)30668-7. DOI: 10.1016/j.jaip.2016.12.005.