A new study published in Clinical Infectious Diseases has found that adverse events from antibiotics cause an estimated 142,000 emergency department visits per year in the United States.

Antibiotics prescribed for respiratory tract infections may be to blame for a large portion of those emergency department visits. Previous research shows that nearly half of the 100 million antibiotic prescriptions written in the community setting each year for respiratory tract infections may be unnecessary.

“For conditions in which antibiotics have questionable benefit, such as many mild upper respiratory tract infections, weighing the benefits of antibiotics with the risks of a serious adverse event will be especially important,” says study author Daniel Budnitz MD, of the CDC.

The researchers stress the important that antibiotics can have serious side effects and should only be taken when necessary. “Physicians need to communicate to their patients that antibiotics are not harmless,” says Budnitz.