If you keep just one oil in the house, it's usually this one. Tea tree is steam-distilled from the leaves of Melaleuca alternifolia, a small tree native to the Australian coast, and its brisk, green, medicinal scent comes largely from a compound called terpinen-4-ol — the marker used to define a good tea tree oil in the first place. Ours is grown and distilled on the farm: nothing added, nothing hidden.

It's the great all-rounder. Reach for it to calm blemish-prone skin, freshen shoes and gym kit, or add a clean lift to a homemade cleaning spray. A little does a lot, so dilute it well before it touches skin, and patch test first.

Good to know: tea tree is at its best fresh. It slowly changes as it meets air and light, so keep the cap firmly on and store it somewhere cool and dark — your oil stays gentler on skin and truer in scent for much longer.