Children who have more antibiotics are prone to allergic asthma, according to a new study by researchers from the University of British, Columbia. Researchers conducted an experiment and found that certain antibiotics that affect intestinal bacteria also had a profound impact on allergic asthma.

During the experiment, researchers gave two antibiotics - streptomycin and vancomycin. They found that vancomycin profoundly alters the bacterial communities in the intestine and increases the severity of asthma in mouse models.

Researchers also gave the same antibiotics to the adult mouse and found that the antibiotics did not have any impact on the mouse. This indicates that early life is a critical period for establishing a healthy immune system.

Allergic asthma affects more than 100 million people worldwide and its prevalence is increasing on average by 50 per cent every decade, particularly among children in industrialised countries, according to the Asthma Society of Canada.

"It has long been suspected that kids exposed to more antibiotics - like those in developed countries - are more prone to allergic asthma," said Brett Finlay, microbiologist at the University of British Columbia. "Our study is the first experimental proof that shows how."

The human gut is colonised by approximately 100 trillion bacteria, and contains upwards of 1,000 bacterial species. While not fully understood, these micro-organisms, known as "gut flora," perform a host of useful functions.

Modern societal practices, such as improved sanitation methods and widespread antibiotic use are causing the disappearance of ancestral species of bacteria in our gut that may be critical to a healthy immune system.

Marc Ouellette, Scientific Director of Canadian Institutes of Health Research's Institute of Infection and Immunity, said: "It has been recognised that microbes play an important role in human health - and we are discovering that a disruption of these bugs is associated with a number of chronic health conditions. The important results from Prof Finlay's team confirm that giving antibiotics to young children, which disturb their normal bacterial flora, should not be taken lightly."