Evening primrose oil (EPO), which contains a group of n-6 series essential fatty acids, is approved in many countries as an adjuvant treatment for atopic dermatitis (AD). Its effective component is believed to be gamma-linolenic acid (GLA). Some authors have proposed that delta-6-desaturase is defective in AD patients1. This defect has been found to cause lower serum concentrations of GLA, dihomo-gamma-linolenic acid (DGLA), arachidonic acid (AA) and prostaglandin E1/E2 (PGE1, PGE2) in AD patients, compared to normal controls2. It has also been claimed that low concentrations of PGE1 and PGE2 play a major role in the pathogenesis of atopic disease3.