English walnuts are implicated in severe, IgE-mediated food allergy in humans. We sought to determine if polyphenolic compounds extracted from the edible nut could promote IgE production to a coadministered allergen. BALB/c mice were sensitized to ovalbumin (OVA) with or without alum (AL) or polyphenolic-enriched extract via intraperitoneal injection. Serum was analyzed for total IgE and OVA-specific IgE, IgG1, and IgG2a/2b. Coadministration of walnut polyphenolic-enriched extract with antigen and AL increased serum concentrations of antigen-specific IgE and IgG1. When AL was excluded from the injections, polyphenolic extract tended to enhance OVA-specific IgE and IgG1 over levels induced by OVA alone, but the increase did not reach significance. Serum IgG2a/2b levels were similar between mice receiving OVA/AL and OVA/AL with polyphenolics. Thus, walnut polyphenolic extract enhanced the Th2-skewing effect of an aluminum hydroxide adjuvant. This indicates that walnut polyphenolic compounds may play a role in allergic sensitization of genetically predisposed individuals.