Why do we "get used to" smells and then can no longer smell them?

Question

For example, I can only barely smell the perfume that I've put on after several minutes pass. Sometimes as I'm getting ready, I wonder if I have already put perfume on or not. Seems like I should be able to tell by smelling it but I can't. The perfume will dissipate but that doesn't explain how hours later, someone may compliment my perfume. It must still be there even though I can't smell it at all.

Another example is how you can walk into a room and be overwhelmed by a smell but then after a minute or two you get "used to it". (Think of cookies baking instead of walking into a restroom.) You might completely forget about the smell that was so strong to you earlier until someone else walks into the room and they comment on the smell.

Answer 1

Because our sense of smell is based on specific receptors that each detect one type of scent (molecule). When those receptors detect their specific scent they react and send a message off to the brain telling us we have detected a certain scent. Once that message has been sent it takes a while for the receptor to "recharge" and get ready to send a new message when needed.

If we detect a VERY strong scent, nearly all of our receptors to that specific smell would send off their message to the brain. IF the smell continues, each receptor as it recharges immediately fires off a new message to the brain. But in such circumstances, for us to "smell" the scent we need a certain number of the messages to be recieved in a short time. When we get the few messages telling us that a certain smell is around to our brain they are at low level, and while you can barely smell your perfume, it may still be a strong scent to someone who has not been exposed to it recently at high levels.

Some smells are complex, and invovle MANY different molecules that are detected by different receptors. Such smells are harder to become used to than "specific" scents like in a perfume. For example when we smell something rotten, we are smelling a lot of different types of scent molecules at once and while some components of our sense of smell may be overwhelmed for specific sent molecules, other components may not be.

Answer 2

All of your senses are filtered. If you were to process everything you saw, heard, smelled, touched, tasted, etc (yes there are more sense) you would go nuts.

If you took a snapshot of what you were looking at right now, it would take hours to really analyze everything. There's probably whole houses, or a big tree, that you pass every day on your way home that you never even notice.

Same goes with smells, there's millions of particles in the air, you wouldn't survive if you spent all your time recognizing all of them.

When you trip on acid, it takes down the filters, which is why people have intense visuals and all sorts of unnatural experiences. You're sensing EVERYTHING.

Answer 3

I don't know the how.. i googled it and didn't get any real help.

My guess on the why is an adjustment to assure that we notice new smells over a smell we've been surrounded by. So that new food or predators would get our attention even if we are sitting in a stinky swamp.

Just a guess though

Answer 4

Geez, all these technical answers. Te process is called sensory adaptation. The "new" smells are detected, then the brain registers them and files them away to the preconscious area, so they do not take up our entire conscious. When we smell the scent again, the brain registers it and brings it back to conscious for recognition.

Answer 5

.....the smell molecules are detected by the olfactory receptors
in the nose.
these olfactory receptor neurons works like
..........."KEY AND LOCK SYSTEM"
when a a molecule of a smell fits into the particular lock of the
receptor,it will respond.
.....this odor information is stored in the long term memory of the brain because the neurons of olfactory are connected with brain .
.....so thats why the nose gets used to the smell if it continues.