Thanks to Skillshare for supporting this episode of SciShow. [♩INTRO].

From the Moruga Scorpion to the Carolina Reaper or even the mysterious Pepper X, adventurous eaters are constantly on the hunt for the next hottest thing. And they might even think they’ve found it, if they’ve tried a drop of pure capsaicin, the potent chemical that gives those peppers their heat.

But the hottest chemical we know of isn’t made by a pepper. It’s a compound called resiniferatoxin. And trust me, you do not want to eat it.

When we say something is “hot” or “spicy,” what we really mean is that it activates heat-sensitive neurons that have a receptor called TRPV1. This particular receptor normally triggers pain nerves to fire when they’re exposed to high temperatures or acids. So spicy things feel hot because your brain actually thinks you’re being burned.

Capsaicin, the main spicy chemical in chili peppers, strongly activates this receptor. And resiniferatoxin, or RTX for short, does what capsaicin does, just better. In lab tests, it’s anywhere from 100 to 10,000 times as potent.

Of course, foodies don’t run experiments in test tubes or petri dishes. They measure spiciness using Scoville Heat Units or SHUs, which are named after their creator, pharmacist Wilbur Scoville. His 1912 paper defines an SHU as how much a pepper extract needs to be diluted before someone can no longer taste it.

So 10 SHUs means the heat is gone after a 1:10 dilution. Using this scale, a jalapeno is about 2,500 to 8,000 SHUs, a Carolina Reaper is 1.5 to 2.2 million SHUs, and pure capsaicin is 16 million SHUs. But RTX blows them all out of the water with a staggering 16 billion SHUs.

That’s Billion with a B! There’s no hot sauce that contains RTX, and that’s a good thing. Scientists estimate eating as little as 10 grams of the stuff, about the same weight as 10 M&Ms, could be fatal.

And it’s considered so dangerous that researchers working with it don gloves and respirators to prevent chemical burns. While it might seem like something so dangerously spicy could only be created by a mad scientist, it’s actually produced by a cactus-like plant native to Morocco. The molecule itself is a diterpene, a kind of carbon-and-hydrogen molecule with lots of double bonds.

That makes it similar to a lot of compounds produced by plants, including ones that fight against microbes, though so far, none of them can match its spicy kick. Weird as it might sound, scientists are looking into using RTX medically, to treat severe pain. That’s because it activates pain-sensing neurons so strongly that they essentially get exhausted.

So they either make themselves less sensitive to the stuff, or die. Either way, you end up with fewer pain signals being sent to the brain. But while the medical potential of RTX is intriguing, it’s a very dangerous substance.

So it’s not something you should try at home, therapeutically, or to spice up your curry. The good news is, if you are looking to spice up your cooking, there are plenty of other ways to do that. For example, you could try a cooking class from Skillshare!

I like this one by culinary instructor Shefaly Ravula, which goes over five techniques for classic Indian cooking. She teaches you things like how to make a good chutney, and how to toast and grind your own spices, although RTX is definitely not on that list. By the end of the videos, you end up with a ton of useful skills that can be applied to all kinds of recipes.

And if you’re already a cooking pro, Skillshare also has more than 20,000 other classes where you can try something new. Right now, Skillshare is offering SciShow viewers 2 months of unlimited access to all their classes for free! Just check out the link in the description. [♩OUTRO].