A new study finds that early exposure to antibiotics kills healthy bacteria in the digestive tract and can lead to asthma and allergies. The findings were reported in Mucosal Immunology.

In this study, five-day-old mice were administered water, azithromycin or amoxicillin. Subsequent to the mice maturing, they were exposed to a common allergen derived from dust mites. The results showed that mice that took either antibiotic, especially azithromycin, demonstrated augmented rates of immune responses, such as allergies.

“The practical implication is simple: Avoid antibiotic use in young children whenever you can because it may elevate the risk of significant, long-term problems with allergy and/or asthma,” said senior author Martin Blaser, director of the Center for Advanced Biotechnology and Medicine at Rutgers via a press release about the study.

“This was a carefully controlled experiment,” said Blaser. “The only variable in the first part was antibiotic exposure. The only variable in the second two parts was whether the mixture of gut bacteria had been affected by antibiotics. Everything else about the mice was identical.