I have to admit that I’m a natural born sucker (in more than one sense, some would argue, and they will be right). I have an irresistible inclination to put things in my mouth to see how they taste, which is why today I’m glad I don’t have a Nintendo Switch. Apparently, Nintendo has coated the Switch’s thumb-size game cartridges with a demonic, bitter compound known as denatonium benzoate since it launched its handheld console in 2017. And it has done it again with the Switch 2’s new $70 cartridges.
The human body has a natural aversion to bitter tastes. It’s a survival mechanism product of millions of years of evolution. Many poisonous substances in nature are bitter, so animals developed a sense of disgust for the flavor. Some humans were able to overcome this to willingly intoxicate themselves with gin and tonics, yes, but bitterness turns out to be a great way to deter kids from ingesting harmful substances and potential choking hazards.
Which is why Nintendo decided to dip its games in this inert, nontoxic chemical. Marketed under the brand name Bitrex, denatonium benzoate is the world’s most bitter compound, 1,000 times more intense than quinine—the compound that gives tonic water its bite. While quinine becomes detectable at 0.77 parts per million, Bitrex registers at just 0.05 parts per million. This means that a single 1-milligram drop of this substance can make an entire liter of water absolutely inedible. Nintendo uses concentrations of 10–50 ppm, ensuring immediate, overwhelming disgust.
What does Bitrex taste like?
Bitrex has a long track record. Its origin story traces back to 1958, when Edinburgh-based pharmaceutical firm T. & H. Smith stumbled upon it while researching local anesthetics derived from lidocaine. The compound’s name blends “bitter” and the Latin “rex” (king), cementing its status as the undisputed monarch of aversion. Initially used to denature industrial alcohol, its applications exploded by the 1970s as a safety additive in household cleaners, automotive fluids like antifreeze and windshield washer (which apparently taste sweet without this additive), pesticides, and even cables, where it gets applied to avoid rodents from chewing on them. Today, it is still widely used in those products and others like marker pens, liquid laundry packets, and cosmetics like nail polish.
The sensory experience is a sharp, lingering bitterness devoid of any other flavor, designed to trigger instant rejection. The bitterness of coffee, pure chocolate, or medications like antibiotics taste like candy compared to a Switch cartridge. “I licked an original Switch game once. Never again,” Switch 2 producer Kouichi Kawamoto told Gamespot. “We don’t want anybody to be at risk of unwanted consumption,” Switch 2 director Takuhiro Dohta told the gaming outlet.
But while the Japanese company has doubled down on this compound for the Switch 2’s cartridges, most toy manufacturers don’t rely on taste aversion to avoid choking hazards. Instead, brands adhere to size regulations, which establish that parts must be over 1.25 inches in toys targeted at kids 3 years old and younger.
Companies like Lego took a structural approach to avoid the effect of potential ingestion with its minifigure heads. From 1978 to 1992, the iconic minifigs featured solid studs on the top of their heads but the company redesigned them with hollow, three-armed lattices to create air passages—a move that mirrored BIC’s pen cap safety holes. The logic was simple: If a child swallowed a head, airflow might prevent suffocation. By 2010, however, Lego abandoned the design, claiming that the tiny holes were ineffective for breathing, which is suspicious to say the least (some people say online it was all a matter of cutting down costs, as the design was more expensive to make than the regular heads).
But I digress. Having learned all this, I’m surprised that there are not more toys that use denatonium benzoate. Why do I know this? I told you, I’m a natural born sucker and none of the toys I’ve ever had or my kid was bitter. While adults might instinctively avoid mouthing cartridges, toddlers are always at risk. The potential for choking for little kids lurks around many homes, as there could be older siblings with toys that have smaller parts even if the toddler’s toys are too big to be ingested. Frankly, as a parent, I’m surprised they don’t sell 5-gallon Bitrex sprays at Walmart to coat the entire bloody house with it.
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