Nintendo Switch cartridges aren’t meant to be put into your mouth but that hasn’t stopped people from doing so. Those that have tasted the cartridges report an extremely bitter taste that’s hard to wash away. Nintendo of America has explained to Kotaku that it’s intentional as they’ve used a bittering agent to stop young children from putting the cartridges they find lying around on the coffee table into their mouths.
“To avoid the possibility of accidental ingestion, keep the game card away from young children. A bittering agent (Denatonium Benzoate) has also been applied to the game card. This bittering agent is non-toxic.”
Thanks to RidleySlayer for the tip!