Tea tree oil

Sharp, medicinal-herbal with a spicy, earthy camphor note.

What it is: Natural oil from steam-distilled leaves.
Where it comes from: Australia (New South Wales)
When you smell it: Top notes: when you spray it.
What perfumers do with it: Signals 'clean' and 'purifying' in skincare and functional fragrance; rarely in fine perfumery.
Worth knowing: Aged, oxidized tea tree oil is far likelier to trigger skin allergies than fresh oil.
Also called: Melaleuca alternifolia leaf oil

Not on the label of any of the 1181 perfumes read so far.