Tea Tree oil is a yellow green essential oil with a fresh camphoraceous odour. Pure Tea Tree oil contains 48 distinct known compounds, two of which are of critical importance: terpinene-4-ol and cineole. Terpinene-4-ol is believed to be responsible for the healing potential of the oil, while cineole lends its antiseptic qualities. Although both of these constituents are natural bactericidal and fungicidal, cineole can be a skin irritant. The cineole / terpinen ratio can vary considerably in the many species of Tea Tree. The ratio can even vary in the same species growing in different areas. For this reason, the Australian Standards Association (ASIA) has established certain criteria to ensure quality in manufacturing Tea Tree oil. According to ASA, quality Tea Tree oil must contain all 48 constituents, unadulterated; the terpinene-4-ol content must be no less than 30% of the entire solution and the cineole content cannot exceed 15% because it can be caustic to the skin.
Typically, most Tea Tree oils found on the market contain from 35% to 45% terpinene-4-ol and 5% to 10% cineole. The natural antiseptic, antifungal, antiviral properties of the oil result from the combination of many of the different compounds working together. There have been several studies that validate claims that Tea Tree oil may be effective in inhibiting a wide range of organisms. Tea Tree oil is also reputed to speed healing, lessen inflammation and pain ameliorating itchy skin reactions.