When we think of deadly poisons, most of our minds will jump instantly to arsenic. George III of England, Napoleon Bonaparte and the Gaungxu Emperor of China are all thought to have died from its effects – either from a deliberate assassination or accidental exposure.

As Dominic Burgess from BritLab explains in the video above, just 200 milligrams– around the weight of a raindrop – is enough to kill someone within two hours. The first sign is a metallic taste in your mouth, followed by vomiting and seizures, and death.

It sounds horrific – but arsenic is positively innocuous compared to the other substances that Burgess profiles.

Consider tetrodotoxin (TTX), a poison found in puffer fish and blue-ringed octopuses that leaves you paralysed as your body goes through some agonising reactions. “Your lips and tongue will begin to burn, your mouth will erupt with saliva and you’ll get very sweaty,” Burgess explains. “You’ll no longer be able to speak, swallow, seizures will begin and your body will slowly shut down – all while you are completely lucid but unable to move.” Death comes after six hours of symptoms and there is no antidote.

The writer and anthropologist Zora Neale Hurston suggested that voodoo witch doctors may have used near-lethal doses of TTX to induce a kind of death-like coma, followed by a zombie-like trance, although scientific evidence fails to support the theory.

Often these poisons are alarmingly close to home. One lethal chemical – cardiac glycoside digoxin – can be found in a common garden flower, while the deadliest can be seen in many hospitals; just 2kg would be enough to wipe out the whole of the human race. Watch the full clip to find out where these chemicals come from and why they are so lethal.


Follow BritLab's YouTube channel and join 700,000+ Future fans by liking us on Facebook, or follow us on Twitter, Google+, LinkedIn and Instagram.

If you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.