Manuka oil is distilled from the leaves of the Leptospermum scoparium tree, which is indigenous to New Zealand and parts of Australia.
Most commercially found tea tree oils are distilled from the leaves of the Melaleuca alternifolia, a tree native to Australia. It is "active against all three categories of infectious organisms: bacteria, viruses and fungi," according to Anitra C. Carr, Ph.D., of the Linus Pauling Institute.
Because of their antiseptic and anti-inflammatory properties, tea tree oils can be used topically to treat conditions such as acne, cold sores, skin inflammations, dandruff and other conditions. As with any medication, consult your doctor if you appear to be suffering any worse or adverse reactions.
While the oils are similar in terms of the properties they offer, the trees themselves have their own unique qualities. For example, the manuka tree--but not the melaleuca tree--produces a type of honey that is being studied for its antibacterial properties.
The name "tea tree oil" originates from the famed British explorer Captain James Cook, who named the tree after learning to brew tea from its leaves, a recipe long practiced by native Australians.