The dietary intake of certain fatty acids might contribute to the development of atopic diseases like allergic rhinitis and asthma. We investigated the association between the ratio of n-6 and n-3 fatty acids in serum phospholipids and hay fever or allergic sensitisation in adults. Data from a population based cross-sectional study on respiratory health including measurement of fatty acids in serum phospholipids of 740 adults between 20 and 64 years of age were analysed. We could not find any significant association between n6/n3-ratio of fatty acids in serum phospholipids and hay fever or allergic sensitisation neither in the total population nor in the sub-population stratified by sex. Since no previous study on fatty acid intake confirmed the n6/n3-ratio hypothesis and this study did not find any association between the n6/n3-ratio in serum-phospholipids and hay fever or allergic sensitization, we conclude that the n6/n3- ratio hypothesis is not confirmed although biological plausible.