Science Questions

Why is it that some smells disappear with continued smelling?

Sun, 14th Sep 2008

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Question

Tim Chiles asked:

Why is it that some smells disappear with continued smelling?

Answer

Kat -  The answer here is something to do with adaptation and desensitisation.  It’s the same reason why you’re not sitting there going, ‘Oh gosh, I’m not wearing clothes! Oh, I’m sitting on a seat!’ all the time.  If that happened, if our nerves responded to every stimulus we’re getting all the time we would just be overwhelmed and wouldn’t know what to do.  What happens if you’re sniffing vinegar or something with a really strong smell?  It goes under your nose, up into your nose and it activates something called olfactory neurons.  These are basically smelling nerve cells up in your nose and they send a signal to your brain that says, ‘This is a really strong smell, this is what it smells like.’  The signals that are being sent by those neurons are in the form of chemicals, little chemical messengers.  They kinda get worn out.  They run out of chemicals in these cells.  Something called desensitisation happens.  You stop being able to smell the smell.  This is very important because say if you’re – if you think back to our ancestors sitting around in the jungle or in their cave – you want to spot new things happening to you.  You don’t need need to know about what’s going on that’s already happening to you.  You want to spot new stuff.  Something like a very strong smell you need to spot it when it’s new and it’s happening so it can be over the level of noise that’s going on around you.  What happens if you’re smelling a strong smell after a while you’ll stop smelling it, basically.  Anyone who’s lived with boys and particularly whiffy toilet habits will know this.

Chris -  The evidence is that men and women make equal amounts of smells, equally often during the day.

Kat -  Yeah, yeah...

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timothy chiles asked the Naked Scientists: When I was in high school we did a test where people where blind folded then items where placed under there nose to smell. One of these test with vinegar I remember well for the person thought the smell was removed but it was still there. Could you explain why...and maybe reference a real study. I appreciate your time. Tim Chiles What do you think? timothy chiles , Sun, 14th Sep 2008

This has been discussed here a few times and I was clearly paying attention because I can't recall the facts !.... ..In fact, it even have been a question that I even asked !

As I recall (loosely)...it's (in very simple terms because that's all I know !! )...it's a matter of your body simply getting used to the smell.

...........this happens a lot with people who work in areas where the odour is really offensive....eventually, the nasal receptors become acclimatised to the smell and this of course interacts with the brain etc etc..

Ok..I'l let someone who can actually explain this in more detail have a go now !! neilep, Sun, 14th Sep 2008

It gets less intense, but it never fully goes away for me. Unfortunately, it is still annoying even with the less intensity. TonyCap, Mon, 15th Sep 2008

Is there any way to beat this, like a way to trick your senses into smelling the odor again? What if you are trying to track down this odor in your house and you can't find it, then it's suddenly gone because you've gotten used to it? Steven Seed, Tue, 11th Feb 2014

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