Giving children antibiotics before their first birthday can increase their risk of developing asthma before the age of seven years, research suggests.
Ania Kozyrskyj and team say that the risk of developing asthma doubled in one-year-olds who received antibiotics for nonrespiratory infections.
The scientists, from the University of Manitoba in Montreal, Canada, monitored the use of antibiotics in 13,116 children from birth to the age of seven years.
Chances of children developing asthma increased with the number of antibiotic courses. Those receiving more than four courses of antibiotics had 1.5 times the risk of developing asthma than those not given antibiotics.
Children who had mothers with asthma or those who lived with a dog also had a higher risk of developing the condition in later life.
"Antibiotics are frequently prescribed for young children for both respiratory and nonrespiratory infections," said Mark Roser, president of the American College of Chest Physicians.
"Understanding the relationship between antibiotic use and asthma can help clinicians make informed decisions about treatment options for children."