The caution comes down to the inherent and well-documented fire risk of lithium-ion and lithium-metal batteries, which some electric toothbrushes use.
Travelers planning to fly with an electric toothbrush in their carry-on luggage might want to double-check their device before heading to the airport. The Transportation Security Administration (TSA) and the Federal Aviation Administration (FAA) have put out a reminder to passengers that devices containing lithium batteries, including many electric toothbrushes, probably need to stay out of their checked bags. That said, they still might be a problem in their carry-on, too.
The reasoning comes down to the inherent and well-documented fire risk of lithium-ion and lithium-metal batteries. Devices with one of these batteries inside can suddenly overheat and ignite thanks to thermal runaway, a chemical reaction that becomes especially dangerous in the pressurized cabin of an airplane. While these incidents are rare, they continue to pose a threat to planes. And if your toothbrush of choice ever gets flagged by the Consumer Product Safety Commission, not even your carry-on would be safe.
