The BBC's Science Correspondent Sue Nelson : "British researchers say, aerosols may harm new mothers and babies"

The study, reported in New Scientist magazine, said that "caution should be advised" on the use of aerosols or air fresheners more than once a week.

The team, based at Bristol University, say they have evidence linking the chemicals found in many sprays to headaches and depression in mothers, and to ear infections and diarrhoea in babies.

In a survey of 14,000 pregnant women, those who used aerosols and air fresheners most days suffered a quarter more headaches than those who used them less than once a week.

There was a increase of 19% in postnatal depression associated with women who frequently used air fresheners.

Many aerosols contain volatile organic compounds

The study also found that babies under six months old exposed on most days to air fresheners had 30% more ear infections than those exposed less than once a week.

Babies frequently exposed to aerosols were one-fifth more likely to suffer from diarrhoea.

Professor Jean Golding, of Bristol University's Division of Child Health, said it was possible, for example, that air fresheners might be used more frequently in homes in which babies were prone to diarrhoea, simply to mask the smell.

No easy explanation

But she said there was no easy explanation for the increase in headaches and ear infections, and that further research was needed.

She said: "A lot of people are unaware that in using air fresheners, you are filling the air with a lot of chemicals.

"The word 'air freshener' sounds like you are purifying things, when in fact you are not doing anything of the sort."

She said the chemicals present in many aerosols, such as xylene, ketones and aldehydes, had been associated with so-called "sick building syndrome".

"What we might be looking at here is the home equivalent," said Professor Golding.

There is no firm evidence of the way in which these chemicals, in low doses, might cause problems, although experiments on mice suggest that the chemicals in air fresheners may weaken the body's defences by making the skin more permeable.

Britain is the biggest producer and user of aerosols in Europe, with the average household buying 36 cans a year.