Apparently, Nintendo had a pretty common problem with their use of cartridges back in the olden days of the Game Boy, and perhaps even still with 3DS titles. They were so small that some children attempted to eat them!
This is funny in one of those “kids do the darndest things” ways, but also very obviously a serious issue that Nintendo wants to prevent if at all possible. After all, someone is very likely to choke on these things if they swallow them.
So Nintendo is trying something new for the Nintendo Switch: they’re making the cartridges taste bad! That’s right — Nintendo actually had to concoct a nasty flavor to coat Nintendo Switch labels with in order to deter children from trying to eat them.
The bittering agent used on the labels is Denatonium Bonzoate, so if your kid does happen to try and add Switch games to their diet it won’t do them any harm. That’s unless, of course, they don’t mind the taste and eat the cartridge anyway, but then you have bigger problems.