Children with runny noses are less likely to develop asthma because colds and infections build up their resistence, a study, published in the British Medical Journal, showed.
Those who had at least two colds in their first year had half the chance of asthma by the age of seven as babies who had just one or none.
Asthma has becoming increasingly common in children, affecting one in seven aged two to 15, and the incidence has doubled among under-fives since 1990.
There is heated debate over whether today's hygienic lifestyles, in which young children are vaccinated and given antibiotics, are contributing to rising rates of asthma.
The findings, published in the British Medical Journal, will bolster the argument that exposing children to common infections can help to strengthen the immune system.
For the study, German researchers followed 1 300 children from birth to the age of seven and recorded the illnesses they suffered.
By seven, six percent of children had been diagnosed with asthma and 10 percent had been wheezing the year before.
In an accompanying editorial, Professor Sebastian Johnston, of Imperial College School of Medicine, said earlier studies showed children from large families or who grow up on farms were less likely to develop asthma than youngsters brought up in more hygienic conditions.
"The challenge before us is to find ways of reproducing the protective effects of early childhood infections, while at the same time reducing the burden of serious (and less serious but still troublesome) infectious diseases."