Dietary supplementation with borage and echium seed oils decreases FcϵRI-dependent cysteinyl leukotriene generation by peripheral blood basophils. Cysteinyl leukotriene generation is shown prior to (●, closed circles) and one week (∆, open triangles), two weeks (□, open squares), and three weeks (○, open circles) after dietary supplementation with one of four borage and echium seed oil combinations (Groups 1–4, respectively) in response to buffer alone, control IgG1 (1.0 μg/ml, IgG), and 15A5, an activating antibody against FcϵRI (0.01 to 1.0 μg/ml). Due to technical errors, data are not available for one subject in each of groups 1, 3, and 4. In addition, basophils from one subject in each of groups 3 and 4 failed to release leukotrienes upon stimulation, a well described phenomenon due to impaired signaling through Syk. Data are expressed as a percentage of maximal cysteinyl leukotriene generation in each subject and are expressed as means ± SEM. Statistically significant suppression of ex vivo leukotriene generation was noted (p < 0.0001) with a significant difference between groups (p < 0.0001).