Your snout is able to determine over 10,000 different smells using about 500 nasal receptors.
However for some people, smell is but a memory.
They are unable to smell a whiff of anything and this total loss of smell is known as anosmia.
It currently affects around 5% of the US population, which means there are around 16 million people unable to smell leaking gas, smoke, or even worse, themselves (resulting often, undertandably, in some level of social anxiety).
As well as that, they sometimes can’t taste the flavours in food.
Your brain portion that controls smell is located at the base of your skull, so even mild head injuries to the back of the head can result in anosmia, however this is often temporary.
But for those whose smell never returns, hallucination of smells can form in their place where people think they smell coffee, smoke or other alarming substances even when there is none.
Hallucinated smells of a particularly vile smell kind are called cacosmia as described by Bonnie Blodgett in her book ‘Remembering Smell’ where she was plunged into a flurry of terrible smells from rotten eggs to chemicals, mould and sick.
On a more positive note, there have been recent studies to suggest that those who have a good sense of smell are more emotionally sensitive (thought to be because the two areas of the brain related to emotion and sense are in the limbic system), and science has taken steps closer to proving the simple truth that a memory can be triggered by a smell due to the proximity of the amygdala (the part of the brain responsible for emotional memory) to the hypothalamus and olfactory tracts (nose!).
So if you can smell the roses, be thankful. Some people are getting noses full of nothing, or worse.
Facts found in Oliver Sacks’ newest book ‘Hallucinations’.
LittleGreyMatters 
