Lemon eucalyptus essential oil is distilled from the leaves of the lemon eucalyptus tree. It is made of several different chemical components, including citronellal, which is also found in other essential oils. Despite being similarly named, lemon eucalyptus essential oil is different from oil of lemon eucalyptus (OLE), which is� often Trusted Source� an ingredient in natural mosquito repellents. OLE is extracted from the leaves of the lemon eucalyptus tree and is enriched for its active ingredient, para-menthane-3,8-diol (PMD).