It is important to remember that essential oils are chemicals too, even though they were derived from plants that grow naturally. Some are potentially hazardous if ingested or applied to wounds, cuts, irritated skin or the mucous membranes of the eyes.
Eucalyptus Oil p-menthane 3,8-diol (PMD)
This plant based repellent uses oil extracted from Eucalyptus trees (E. citriodora) as its active ingredient (PMD). This has been the most commonly used repellent in China for more than 20 years. PMD has been identified as the compound that provides the strongest protection from insects in this plant. In 2000, the US EPA registered this compound for use in the United States. PMD is the active ingredient in Quwenling, a repellent product made in China. Products containing PMD are relatively new to the U.S. market. There are special warning labels on products containing PMD advising users not to get the product in their eyes and to avoid spraying directly on or near the face. Users are also advised not to use PMD on the faces or hands of small children. PMD is not to be used on children younger than three years of age.
Citronella Oil
Approved and registered for use in 1948 by the EPA as a repellent, Citronella Oil is derived from Citronella grass (Cymbopogon nardus). There have been no reports of serious adverse reactions to dermal applications at label rates. Testing has shown that it is moderately effective and also short lasting when applied to the skin. Candles and space sprays are largely ineffective as repellents.
Currently the Centers for Disease Control and Prevention (CDC) recognizes and recommends the use of DEET, Picaridin and Oil of Lemon Eucalyptus as effective in repelling mosquitoes and reducing the chances of contracting West Nile Virus and other mosquito-borne diseases.