Venomous or poisonous: what’s the difference?

I often hear about poisonous snakes. However, the dangerous snakes which I am likely to encounter are venomous. So is there a difference between the meanings of the words ‘poisonous’ and ‘venomous’?

The bulging gland on the back of this Cane Toad, indicated by the arrows, contains poison.

Yep, there’s a difference

An animal is considered venomous if it’s capable of injecting venom. It could be injected out of fangs or from a sting. So venomous creatures include snakes, spiders, wasps, jellyfish, stingrays and plenty more critters which you don’t want to get too close to.

The Smooth Toadfish is considered poisonous because eating its flesh can be fatal to humans

The fangs of a Huntsman Spider are designed to deliver venom

Many types of fungus are poisonous

This extreme close-up shot shows the formidable stinger of a Jumper Ant. If you look carefully you can see the hollow centre, through which it delivers its venom

It’s not correct to call all of those animals poisonous, because the word poisonous has a different meaning.

The simplest way to understand the meaning of the word poisonous is to say that something is considered poisonous if it’s dangerous to eat it or to breathe it. For example, many types of mushrooms are poisonous. Some mushrooms can make you very sick or even kill you if you eat them. You would never hear about ‘venomous mushrooms’. The stuff which comes out of the glands on a Cane Toad’s back is poisonous too, but you wouldn’t call Cane Toads venomous.

Some fish can be venomous or poisonous

Some fish, like Stonefish, are venomous, because they have venom which can be injected from spines in the dorsal fin, while other fish like the Smooth Toadfish are poisonous because they can kill you if you eat them.

Okay then, so is venom poisonous?

There’s an old joke:

Two snakes were in the grass and one snake said to the other, ‘Hey, are we venomous?’

The other snake said, ‘Sure we are. Why do you want to know?’

The first snake said, ‘Because I just bit my tongue.’

I don’t know about a snake biting its tongue but I think it’s self-evident that a snake is able to swallow something it bit without being made sick by it. But what about us? Would venom be poisonous to humans?

Now we know that poisons are bad if you breathe or eat them, while venom works from being injected. But both types of substance are bad for you despite working (and being delivered) in different ways to the victim. I’ve read stories about people eating venomous spiders and I don’t doubt it happens when people fully understand what they are doing. Perhaps the venom was neutralised by cooking but I don’t know enough about that so I personally won’t be trying it. One thing which would be stupidly dangerous would be to eat a live venomous spider because the spider would almost certainly bite you in your mouth or throat and therefore inject its dangerous venom.