Why do the farts of others smell worse?

15 April 2014

Question

Why does someone's air biscuit, or the technical term for flatulence, why does that smell bad from someone else when it's not so bad when you smell your own?

Answer

Hannah - Well, I would say that my farts really are quite stinky even to myself and I asked my boyfriend about this and he agreed. But he said that his own farts, he found curiously pleasant - was his expression.

Chris - Is everyone universally in agreement here in the studio?

Hannah - Not about my farts, about your own.

Helen - I think it's particularly bad if it's someone else's because it's more the thought really that it's not come out of yourself, your own body. And maybe, is it a similar thing to other sorts of bodily fluids like - I don't know - mothers get very used to their children's puke and poo, and all sorts of things because they kind of have to. But if it was another child's puke and poo, I'd presume they wouldn't be quite so pleased of getting close to it.

Hannah - There have been scientific studies on farts and also, baby's poo. In a blind study, mothers find their own children's poo more pleasant smelling than other children's poo and the same can be said of people's farts. So, just imagining the smell of your own farts, people rate it as okay, but if you're asked to imagine the smell of anyone else's fart then yeah, they think it's disgusting and it's possibly...

Chris - I was going to say, one theory I heard of this is that one person pointed out to me that one possibility is that the gases that you're going to release don't just come out of you, out of your rear end. Effectively, those volatile chemicals go into your bloodstream a bit and that means they get carried up to the receptors in your nose via your bloodstream and they desensitise the receptors in your nose a little bit. You effectively get used to the smells you're going to make and this means that because you've been smelling it already, it doesn't smell quite as offensive to you because it's less new to you compared with someone else who's having to put up with it for the first time. Ramsey...

Ramsey - Similarly Chris, I believe that our sense of smell is relative. So, we get used to smells in other words. So, when you come home from holiday and you open your door to your house and you sort of think, "Oh, it smells a bit musty. I'm going to go and open some windows." It might not actually be a musty house at all. That is the smell of your home. You just normally get used to it and I think we all probably know people who we think smell a lot like their dogs, or generally, smell a bit funny in general and you kind of think, how does this person not notice they're a bit smelly. Well, we all get used to our own smells and it's because it's a relative sense that we have.

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