<ul>
<li>Odour molecules that move through the air up your nostrils will bind to special smell receptors on the surface of nerve cells. </li>
<li>The nerve cells send a signal to the brain's olfactory bulb, that is behind the bridge of the nose.</li>
<li>People have about 400 different smell receptor types. </li>
<li>The odour molecules create a pattern of activation in the nerve cells that the brain translates as a smell.</li>
</ul>

How smell works

A complete loss of smell, known as anosmia, can occur after a cold, sinus infection or even a bump to the head.
Anosmia affects the flavour of food. However, it isn't always permanent and may recover naturally or through exercises like 'smell training' to re-stimulate the olfactory system.

When we lose our sense of smell

<ul>
<li>Smells can alert us about danger - we're repulsed by the smell of sewage and rotting food.</li>
<li>We don't all respond to odour molecules in the same way. </li>
<li>Butyric acid contributes to the smell of both Parmesan cheese and vomit, so it may smell offputting or appealing, depending on the situation.</li>
</ul>

How we react to certain smells

We teamed up with the folks behind BBC World Service’s CrowdScience to answer your questions on one topic - this week it's all about smell.

How we react to certain smells

What’s in a smell?

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