Further studies are needed to evaluate whether changes to the diet can reduce manifestation of the disease.

Hay fever, an allergy to pollen, is the most common form of allergy in the UK, affecting up to 20 per cent of the population. It affects more than 26 million Americans each year and is expected to affect growing numbers as global warming takes hold.

The team from the German Cancer Research Center in Heidelberg, Germany selected 334 people with adult onset hay fever from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Heidelberg cohort and matched them with 1336 controls. They used validated food frequency questionnaires to record data on the subjects' diets.

Writing in this month's issue of Allergy (vol 58, issue 12, p1277), the scientists report a positive association between high intake of oleic acid and hay fever whereas high intake of eicosapentaenoic acid was inversely related to the symptoms. High intake of beta-carotene also increased the risk of hay fever while vitamin E showed a protective factor.

But the researchers note that in grouped analyses, the effects of beta-carotene and vitamin E were mainly observed among women and former or current smokers; in these subgroups, linoleic acid increased the risk of hay fever. These findings "may suggest different biological mechanisms for the investigated nutrients, which need further research", says the study.

Both antioxidants and fatty acids have been shown to play an important role in fighting other diseases.