Olfaction, also known as olfactics, is the sense of smell. This sense is mediated by specialized sensory cells, called olfactory receptors, in our nasal cavities.
Olfaction – the detection of smells – occurs when odorant molecules bind to specific sites on these receptors. These receptors come together at the glomerulus, a structure that transmits signals to the olfactory bulb (a brain structure located directly above the nasal cavity and below the frontal lobe).
Olfaction, along with taste, is a form of chemoreception. The chemicals that activate the olfactory system, generally at very low concentrations (meaning you can smell something even if there is very little of it) are called odorants.
Humans have two “chemical” based senses – smell and taste. We have just five established basic tastes: sweetness, sourness, saltiness, bitterness, and umami (or savory).
But, while fleeting, there are hundreds of olfactory receptors for smell (some 388 according to one source), each binding to a particular molecular feature. Odor molecules possess a variety of features and, thus, excite specific receptors more or less strongly. This combination of excitatory signals from different receptors makes up what we perceive as the molecule’s smell. So each of us will perceive a perfume differently. A bit more of the one molecule, or a bit less of the other in a fragrance, means that one person would interpret it one way, and another person in quite a different way.
This is why designing perfumes is both an art and a science, both of which the perfumier (the perfume composer or formulator) uses to create the most beautiful, memorable and evocative fragrances.