Allergenicity of gourmet nut oils processed by different methods

Abstract

Background: No information is available on allergenicity of tree nut oils, and information on peanut oils has been conflicting. Many of the nut oils now on the market undergo minimal processing and may contain residual antigen. Objective: This study was carried out to determine whether several of the new “gourmet” tree nut oils, as well as peanut oils, contain residual proteins that could bind IgE from sera of patients with allergy. Methods: Several brands of walnut, almond, hazelnut, pistachio, and macadamia nut oils were examined. Peanut oils, both unrefined oils (which have been shown to contain allergenic proteins) and refined oils (without previously demonstrable allergens), were also examined to confirm reproducibility of immunoreactivity as reported by other investigators. Oils were extracted with 0.2 mol/L ammonium bicarbonate, and protein concentrations in the aqueous extracts were measured. IgE binding was assayed by slot-blot and Western immunoblotting. Pooled sera from patients with a history of systemic reactions to various tree nuts or peanuts were used as appropriate. Results: The oil extracts known to be from oils that had undergone less processing at lower temperatures tended to demonstrate qualitatively greater IgE binding and higher protein concentrations. Conclusion: Tree nut and peanut oils may pose a threat to patients with allergy, depending on the method of manufacture and processing. (J Allergy Clin Immunol 1997;99:502-6.)