Scientists have found one more reason to keep children, especially new borns, off antibiotics. While its well known that antibiotic use disrupts the normal growth of gut bacteria, a new study shows that it could also cause permanent damage to the lungs’ immune system.

The researchers from the Cincinnati Children’s Hospital in the United States conducted experiments in mice for two years to see how the new born lungs and their immune system develops. The researchers wanted to see how a lung’s immune system reacts to gut bacteria being wiped out of the body. The study found that once antibiotics purge good bacteria from the system, there is an adverse effect on molecular signals that tell the lungs to build immune cells, how many cells should be the lungs needs and where they should be deployed.

“The problem is when antibiotics wipe out good bacteria, they cut off that important flow of signals,” the research team said in a statement. “As a result, the lungs build weaker castle walls with fewer guards on duty.”

The short-term disruption in gut bacteria made the mice in the experiment more prone to pneumonia and also made them more likely to die from it. In the long term, continued disruptions to gut bacteria appeared to cause permanent immune system damage. If the antibiotic use is limited, an infant would have some time to replenish the good gut bacteria but the process takes months and resulting microbiome may not have the normal mix of bacteria.

The researchers said that this outcome of excess antibiotic use may explain why some people with no obvious genetic risk factors develop asthma or other lung diseases later in life. Data from the study, which was published in Science Translational Medicine this month, also explains the association between the widespread use of antibiotics and an increased risk of pneumonia in newborn infants.

The researchers will pursue clinical studies to evaluate the safety and benefits of limiting antibiotic use among expectant mothers and newborns, especially the practice of prescribing antibiotics to women before they have C-sections.