The essential oil of the lemon-scented gum mainly consists of citronellal (80%),[3]produced largely in Brazil and China.[4] While unrefined oil from the lemon eucalyptus tree is used in perfumery, a refined form of this oil is used in insect repellents, especially against mosquitoes. The refined oil's citronellal content is turned into cis- and trans- isomers of p-menthane-3,8-diol (PMD), a process which occurs naturally as the eucalyptus leaves age. This refined oil, which includes related compounds from the essential corymbia citriodora, is known widely by its registered tradename, "Citriodiol", but also by generic names which vary by country or continent: "oil of lemon eucalyptus" or "OLE"(USA); "PMD rich botanic oil" or "PMDRBO"(Europe); "PMD and related oil of lemon eucalyptus compounds" (Canada); Extract of Lemon Eucalyptus (Australia). Pure PMD is synthesized for commercial production from synthetic citronellal. Essential oil refined from the leaves of the tree can contained up to 98% citronella content. The smell of the essential oil can vary, but mostly includes a strong odor compatible alone to citronella oil, with a slight hint of lemon scent.