Children are apparently accidentally swallowing them.
Two new studies find the risk has gone up 7 times from 1985 to 2009.
Experts say it's worse than swallowing a coin.
Typically, ingestion results in the battery getting lodged in the esophagus rather than air passages. There is no choking but symptoms can be flu-like, including vomiting, fever, cough and lack of appetite.
There is also a risk of a potentially fatal alkaline burn. Authors reporting in Pediatrics say items that contain these batteries need to be secured with a screw. And parents need to be careful by keeping these out of reach.