The Nintendo Switch is designed to be portable, so it doesn’t have a disc drive. Instead, its games come on cartridges, just like games for Nintendo’s handheld platforms stretching back to the original Game Boy. But there’s something different about Switch cartridges: They taste awful.

Over the past week, reviewers at various outlets have been gamely putting Switch cartridges in their mouths in the name of science and journalism. The investigations seem to have been inspired by Giant Bomb co-founder Jeff Gerstmann, who tweeted a public service announcement last week warning people about the hazards of putting your tongue on a Switch cartridge:

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

Gerstmann actually did that live on camera during Giant Bomb’s Feb. 24 Unprofessional Friday stream. While that series is available exclusively for Giant Bomb subscribers, a viewer captured a clip of the taste test and posted a GIF to Reddit that you can see below.

The reaction is almost immediate — Gerstmann puts the game in his mouth, and after about a second, his face turns sour and he quickly removes the cartridge.

We did our own testing, and can confirm Gerstmann’s instant analysis and advice: DO NOT put Nintendo Switch game cards in your mouth. For one thing, they may be small enough to pose a choking hazard. But regardless of whether the cartridge gets stuck in your throat, its awful taste will certainly linger on your tongue.

First, let’s get through some older game cartridges. Intrepid reporter Julia Alexander tried tasting cartridges from the Nintendo DS, Nintendo 3DS and PlayStation Vita. None of them had any particular taste. (We should note that we were unable to try cartridges that were fresh out of the box for these older platforms.)

After all that, Julia went for it with a copy of Just Dance 2017, a Switch launch title. Here is how she described the sensation:

It doesn’t hit you at first. It tastes just as plain and feels just as slippery as the other three cartridges. In just a few milliseconds, though, a very sour taste invades your taste buds. It smells bad; you can feel it in your throat. It’s revolting, and the only thing I can equate it to is when you’re at the dentist and a drop of sour cleaning material hits the back of your tongue. Your entire face feels it. And the taste lingers for about 20 seconds.

People have speculated that the manufacturing process for Switch cartridges involves coating them in a layer of foul-tasting film, so as to discourage people from, well, putting the cartridges in their mouths. (Why do you think Play-Doh is so bitter and salty?) We’ve reached out to Nintendo to ask why Switch cartridges taste so bad, and we’ll update this article with any information we receive.

In the meantime, we’ll be washing out our mouths with soap to try and get rid of this terrible taste. For more on the Switch, you can read our review.

Update (March 2): In a statement emailed to Polygon, a Nintendo representative confirmed the theory that Switch cartridges are coated in a material that’s meant to dissuade people from putting the units in their mouths.

“A bittering agent (Denatonium Benzoate) has also been applied to the game card,” the spokesperson said, adding that Nintendo recommends keeping Switch cartridges away from children “to avoid the possibility of accidental ingestion.” The representative also noted that denatonium benzoate is non-toxic.

So what is denatonium benzoate, anyway? We did some research.

Denatonium is the most bitter chemical compound known to humanity. It is widely used as an aversive agent, an additive that discourages ingestion by making a substance taste so bad that you’ll immediately want to spit it out.

denatonium benzoate is about 1,000 times more bitter than quinine

Here’s how an episode of Chemistry World’s Chemistry in its Element podcast described denatonium: “If you have something that may be consumed but shouldn’t be, you add some denatonium benzoate and even small quantities of it will put people off.”

Aversive agents are often added to products that are poisonous to humans, like antifreeze, paint and household solvents, to discourage consumption. Denatonium is commonly used to denature ethyl alcohol — that’s where it gets its name — so it cannot be used as drinking alcohol. It is also used in special kinds of nail polish, to prevent people from biting their nails.

If you find quinine disgusting, denatonium benzoate is about 1,000 times more bitter, according to Chemistry World. That means that just a tiny amount is necessary for this purpose. Denatonium benzoate concentrations of only 20-50 parts per million — that’s 0.002 percent to 0.005 percent — get the job done as an aversive agent, according to a 1992 report from the U.S. Consumer Product Safety Commission.

Watch: Nintendo Switch Hardware Review