The active chemical used in spray tans -- called dihydroxyacetone, or DHA -- has been shown in scientific studies to cause genetic mutations, according to a report from ABC news.
However, health experts say the findings are concerning, and that more research on spray tanning is needed.
"These compounds, in some cells, could actually promote the development of cancers or malignancies," Dr. Rey Panettieri, a toxicologist and lung specialist at the University of Pennsylvania, told ABC news.
The problem is that when the chemical is sprayed on, it can be inhaled into the lungs.
DHA is then absorbed into the bloodstream, where it could damage DNA and cause tumors.
The FDA has approved DHA for external use only, meaning it should not be inhaled or ingested, or applied to the lips or eye area.
"Nobody ever thought when it was initially approved as a lotion that people would be spraying it in a room," Dr. Donald Morton, of the John Wayne Cancer Institute, told KTLA.
In fact, tanning booths that offer full body spray tans are not FDA approved.
Dr. Morton said he understands the frustrations of people who have switched to spray tanning as an alternative to lying out in the sun.
"If anything, I think tanning outside is safer," Morton said, a statement that may come as a surprise to many.
The FDA recommends that people protect their eyes, mouth and nose when getting spray tans.
ABC's investigation revealed that many employees at tanning salons were misinformed about the safety of DHA.
It also found that the employees did not offer customers the proper protection.
The tanning industry says it will provide new training, and will make sure customers know about the FDA recommendations.