The proportions of linoleic acid in total plasma lipids and phospholipids were significantly greater and those of oleic acid were lower in pre-puberal and puberal atopic patients as compared with age-matched healthy controls. The n-3/n-6 fatty acid ratio of the triacylglycerol fraction was also lower in atopic patients. However, no significant decreases in the proportions of dihomo-gamma-linolenic acid and arachidonic acid were observed in plasma lipids of atopic patients, suggesting that delta 6-desaturase activity is not impaired in atopic patients. We provide an explanation for the beneficial effects of raising the n-3/n-6 ratio of dietary oils in the context of suppressing allergic hyper-reactivity in humans.