A five year study funded by the British Lung Foundation and the National Asthma Campaign found that pregnant women who suffer from allergies are more likely to have babies who develop allergies and asthma.

However, the researchers also found that it is possible to minimise that risk by reducing a woman's exposure to allergens while she is pregnant.

Dr Jill Warner, who headed the research at Southampton General Hospital, said: "Our research shows that mothers can influence whether their baby develops sensitisation to allergies.

"Controlling the mothers' reactions to allergens especially during the second and third trimesters of pregnancy may well be the treatment of the future, alongside more established advice such as giving up smoking and cutting down on alcohol."

Blood samples

The researchers studied blood samples from premature babies to determine their immune response to common allergens such as household dust and grass pollen.

They found that, from the day they are born, babies who go on to become allergic have an altered immune response which makes them react more strongly to allergens.

The researchers also discovered that babies are able to recognise common allergens their mothers are exposed to in the home while they are still developing in the womb.

An analysis of a group of more than 100 under-fives found that the higher the number of positive allergy tests registered at the age of one, the greater the chance that a child would develop asthma by the age of five.

Forty per cent of those children with at least one allergic asthmatic parent developed asthma.

Ways to reduce risk

The study has analysed ways to reduce allergens in the home effectively.

The researchers advise that a combination of a dehumidifier and a high efficiency vacuum cleaner is most effective in reducing concentrations of allergens in the home and improving asthma symptoms.

Anne Bradley, Chief Executive of the National Asthma Campaign, commented: "With asthma increasing in prevalence, especially among children, this research is potentially of great significance. It adds a valuable contribution towards possible prevention through early intervention whilst also making real inroads towards a possible future cure."