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Have you ever seen a celebrity and wondered:. How do they maintain such a smooth, youthful forehead?

Chances are, that celebrity is using a little Botox. Botox is a prescription drug best known for its cosmetic use, to make wrinkles less noticeable. It’s pretty run-of-the-mill nowadays, but what people might not know is that its active ingredient is one of the deadliest biological substances known to mankind.

That neurotoxin, called botulinum toxin, is produced by the bacterium Clostridium botulinum. We think the first person to try and figure out how it works was German physician Justinus Kerner. In the early 1800s, he observed muscle weakening, gastrointestinal problems, and eventually respiratory failure in patients who had eaten spoiled sausages.

So he figured there must be some kind of poison in the meat that was interfering with their nervous systems. Half a century later, German physician John Muller called this illness botulism, because botulus means sausage in Latin. And then in 1895, the Belgian bacteriologist Émile van Ermengem was investigating a botulism outbreak and traced it back to some cured ham.

He found C. botulinum in the ham and in the tissues of a couple people who died from the disease. And, upon further investigation, he isolated botulinum toxin for the first time. Even today, botulism is usually caused by contaminated food, and that can even be vacuum-sealed packages, because C. botulinum thrives without oxygen.

If you’re unlucky enough to eat it, the bacterium produces botulinum toxin in your gut, which gets absorbed into your bloodstream and makes its way to your peripheral nervous system. Normally, the neurotransmitter acetylcholine is released at the neuromuscular junction, the space or synapse between a neuron and a muscle cell. There, it’s taken up by specific receptors on muscle cells, which makes the muscle contract.

But botulinum toxin blocks the release of acetylcholine, and stops muscle contraction. Yep, those smooth foreheads and cheeks you see in Botox recipients are because of muscle paralysis. If you’re exposed to a dollop of botulinum toxin, weakening of facial muscles usually happens first, and then that spreads throughout your body.

And without treatment, botulinum toxin will eventually affect muscles that you need to breathe. Typically, that treatment includes hospitalization, with antibiotics to kill the bacteria and an antitoxin to take care of the botulinum toxin. So there are some serious risks linked with Botox, but the prescription dose is so low that new nerves can sprout within a couple of months.

And those shiny new synapses mean muscles can contract again. Now, you might be wondering who would ever inject a deadly poison into their face… on purpose? The history of Botox is a little contested, but the first reported use of botulinum toxin in a clinical setting was in the late 1970s.

At that point, it had been purified from C. botulinum and researchers had shown that injecting small amounts could relax overactive muscles. So the opthamologist Alan Scott figured that it could also be used to relax muscles around the eyes, to treat a condition where they’re misaligned called strabismus, which causes problems with vision and depth perception. Injecting this neurotoxin weakened the muscle contractions that were causing his patients’ “cross-eyed” appearance.

And it kept them from needing invasive surgery. Botulinum toxin was also used to treat blepharospasm, a condition where patients can’t always control their eyelids closing. And in the 1980s, ophthalmologist Jean Carruthers was doing that treatment, and noticed the skin around one of her patient’s eyes and forehead got a little less wrinkly.

In a potentially risky move,. Carruthers went ahead and injected the frown lines of her receptionist, marking the first cosmetic use of botulinum toxin. After much more testing to figure out how much botulinum toxin was safe to administer and where, Botox was approved by the FDA on April 15, 2002.

Beyond its cosmetic uses, researchers are looking into the muscle-relaxing quality of Botox for medical purposes. Like, certain injection sites seem to help with chronic migraines and excessive salivation. Or specific muscle groups can be targeted to lessen the movement problems that come with disorders like multiple sclerosis and cerebral palsy.

And that list is only growing. Because Botox is an FDA-approved drug, it can be prescribed by a licensed physician for any condition. That being said, the safety and effectiveness of Botox to treat many medical problems hasn’t been established by the FDA yet.

So there’s a lot of ongoing research to better understand the short-term and long-term risks. For now though, the take-home message is: inject at your own risk. And whether you’re staving off forehead wrinkles or looking to avoid migraines,.

Botox is another amazing example of human ingenuity: re-engineering a deadly toxin for potential good. Thanks for watching this episode of SciShow! If you want to learn more about deadly toxins we’ve co-opted as medicines, check out our list show where we talk about 7 of them.

And if you just want to learn about all kinds of weird science with us, you can go to youtube.com/scishow and subscribe. [♪ OUTRO].