Some young children with persistent wheezing develop asthma, while others do not. It's the presence of an allergy during the first three years of life that seems to make a difference, researchers found.

Young children who experience an allergic reaction to pet hair or dust mites and also suffer persistent wheezing are more likely to develop asthma, researchers say.

Sabina Illi of University Children's Hospital in Munich, Germany, analyzed the health records of about 1,300 children from their birth in 1990 until age 13.

Parents were interviewed about their children's asthma, and measurements were taken of immune system antibodies in the blood linked to asthma.

Children who suffered persistent wheezing and had also developed sensitivity to allergens by age three were more likely to develop a loss of lung function and asthma, the team reported in Saturday's issue of the medical journal The Lancet.

Future research could look at whether giving wheezy, allergy-susceptible children preventive treatment with corticosteroids inhaled from a puffer might reduce the chance of developing asthma at school age, the study's authors said.

On the other hand, about 90 per cent of children who experienced repeated wheezing, but were not susceptible to allergies, lost their lung symptoms at school age.

"Given the good prognosis for non-atopic [non-allergy susceptible] wheezing children, the need for these individuals to continue to take inhaled corticosteroids on a regular basis should be reassessed," the researchers concluded.

The Commission for Environmental Co-operation estimates that about 2.5 million Canadians have asthma.