Feather pillows could be better for people with asthma than synthetic ones, according to research.

The findings contradict previously accepted wisdom which said that man-made pillows caused less allergic reactions.

But now researchers at Wythenshawe Hospital, Manchester, say that levels of cat and dog allergen - products which cause allergic reactions - are seven to eight times higher respectively in synthetic pillows than in feather ones.

Earlier research by the same team found that synthetic pillows contained higher levels of dust mite allergens.

In the latest study, they looked at 14 sets of synthetic and feather pillows used on the same bed over two years.

They concluded that the closely woven fabric around feather pillows - to keep the stuffing from falling out - was probably responsible for the lower levels of allergens.

Overall increase

Dr Adrian Custovic, a member of the British Thoracic Society and one of the team who carried out the study, said: "Previous research has suggested that around half of the overall increase in asthma could be explained by the use of synthetic pillows.

"Tightly woven or allergen-proof materials should be used to encase both synthetic and feather filling in pillows to provide an effective barrier against allergens. It is possible that this could be of real benefit to asthma sufferers."

A spokesman for the National Asthma Society said it advised people who have an allergy to feathers to use synthetic pillows. Following the findings of the study, he added: "We are still advising people to use a good barrier cover with feather pillows."

And he said that as some people have a specific allergy to feathers, it would not be suitable for them to use that type of pillows even with a strong covering.