Tea tree oil is derived from the leaves of the tea tree. The tea tree was named by eighteenth century sailors, who made tea that smelled like nutmeg from the leaves of the tree growing on the swampy southeast Australian coast. Do not confuse the tea tree with the unrelated common tea plant that is used to make black and green teas.

Tea tree oil is applied to the skin (used topically) for infections such as acne, fungal infections of the nail (onychomycosis), lice, scabies, athlete's foot (tinea pedis), and ringworm. It is also used topically as a local antiseptic for cuts and abrasions, for burns, insect bites and stings, boils, vaginal infections, recurrent herpes labialis, toothache, infections of the mouth and nose, sore throat, and for ear infections such as otitis media and otitis externa.
Some people add it to bath water to treat cough, bronchial congestion, and pulmonary inflammation.