10 Chemicals You Really SHOULD Be Scared Of

And now onto some naturally-occurring deadlies, the first of which comes from the seeds of a tree. How bad can that be? We know that berries can be poisonous, and of course mushrooms - but deadly seeds?

If they come from the strychnine tree, then yes. Strychnine is an old poison - the dangerous nature of the tree and its seeds have been known for thousands of years - but the substance itself wasn't isolated until 1818.

It's very poisonous to humans - just a few grams inhaled or swallowed can be deadly. It was once used control pests since it quickly kills rats and mice, and even larger creatures such as moles and coyotes. Of course, there are problems with this - it also kills cats and dogs. And small children. So these days safer methods are used, and strychnine is appropriately difficult to get hold of.

The symptoms of strychnine poisoning include muscle spasms, seizures, stiffness, hyper-vigilance and agitation. It can cause a dramatic curving of the spine and neck, and ultimately it paralyses the respiratory muscles leading to respiratory failure and brain death.

Interestingly, some of those symptoms were seen as quite beneficial, resulting in strychnine's use - in low doses - as a performance-enhancing drug. H. G. Wells mentions it in his 1897 novella, The Invisible Man, when the eponymous character comments that it will "take the flabbiness out of a man." Dabbling with strychnine is a dangerous business though, in a letter written in 1896 a medical student famously describes almost poisoning himself with the stuff.

So now you know. Beware flat, brownish seeds that look a little like dried apricots which have been forgotten at the back of the kitchen cupboard. And next time someone suggests that something is good for you because it's "natural", you can reply with "yeah, like strychnine."