Five facts about smell (2014)

7 hours ago

Humans have three chemical senses: smell, taste, and trigeminal, with trigeminal receptors detecting irritants like mint or chili.
Anosmia, a lack of sense of smell, affects about 1.5% of people, including the author, who shares personal experiences of shame.
Some compounds, such as those in grapefruit, are detectable at extremely low concentrations, with grapefruit being 3.2 million times 'smellier' than lemon on average.
In perfumery, there are seven primary odour categories, but as an anosmic person, the author admits to not knowing these smells firsthand.
The mechanism of smell is not fully understood, with theories including shape theory and vibration theory, and humans may detect up to 1 trillion scents.

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