Also known as Melaleuca, from the name of its native Australian plant source, Melaleuca alternifolia. Tea tree oil has skin-soothing properties and is also an antioxidant. However, as with most fragrant plant oils, tea tree oil contains volatile components (such as linalool, limonene, and eucalyptol) that can be sensitizing, particularly if you apply 100% pure tea tree oil.
For improving skin concerns such as breakouts, tea tree oil concentrations of 2.5% to 10% are recommended. However, the amount present in most skincare products is usually less than 1%, as higher amounts impart a strong scent many people find intolerable, not to mention these higher amounts increase tea tree oil’s potential to sensitize and redden skin.
Careful use and storage of tea tree oil is advised; like all plant oils, it should be protected from routine exposure to light and air. Tea tree oil’s potential to sensitize skin increases when it is exposed to air because the oxidation makes the volatile components more potent.
References for this information:
International Journal of Dermatology, July 2013, pages 784-790
Journal of Food and Drug Analysis, June 2013, pages 169-176
Chemical Research in Toxicology, March 2012, pages 713-721
Australasian Journal of Dermatology, May 2007, pages 83-87
Indian Journal of Dermatology, Venereology, and Leprology, January-February 2007, pages 22-25
Clinical Microbiology Reviews, January 2006, pages 50-62