Each year, at least 4 million Americans experience some sort of adverse reaction to prescription medications, some because they didn’t read the extra labels pasted on the bottles.

The reactions could be avoided if warning labels were more effective, according to a Michigan State University study.

The study revealed only half of the participants surveyed looked at the warning label and 22 percent didn’t look at any labels, says Laura Bix, associate professor in Michigan State’s School of Packaging. She concludes some relatively simple changes could improve the labels’ effectiveness.

“Our initial recommendations would be to move all of the warnings from the colored stickers to the main white label,” she writes in her report.

The change is especially important on prescriptions used by patients 50-plus, Bix said.

“Students in our study tend to rotate the vial and actively search for information. Older folks assume they are going to know what’s on there, so they don’t read it.”