Kotaku recently contacted Nintendo to ask them why Nintendo Switch cartridges taste so awful. Nintendo replied: “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.”
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According to Wikipedia, denatonium benzoate is the most bitter chemical compound known, commonly used as an aversion agent to prevent accidental ingestion, which is why the Switch cards are coated in it. It’s also used in animal repellent, shampoos, soaps and nail-biting prevention.
I put that Switch cart in my mouth and I'm not sure what those things are made of but I can still taste it. Do not try this at home.
— Jeff Gerstmann (@jeffgerstmann) February 25, 2017