Citronella oil is also a plant-based insect repellent, and has been registered for this use in the United States since 1948. The United States Environmental Protection Agency considers oil of citronella as a biopesticide with a non-toxic mode of action. However, since citronella insect repellant effects were not proven within the EU, the use of citronella as an insecticide is prohibited under the Biocidal Product Directive 2006.
Research also shows that citronella oil has strong antifungal properties, is effective in calming barking dogs, and has even been used as a successful spray-on deterrent against pets destroying household items.
The higher proportions of geraniol and citronellal in the Java type make it a better source for perfumery derivatives. The name Cymbopogon winterianus is given to this selected variety to commemorate Mr. Winter—an important oil distiller of Ceylon, who first cultivated and distilled the Maha Pangeri type of citronella in Ceylon.
Both types probably originated from Mana Grass of Sri Lanka, which according to Finnemore (1962) occurs today in two wild forms--Cymbopogon nardus var. linnae (typicus) and C. nardus var. confertiflorus. Neither wild form is known to be used for distillation to any appreciable extent.
Direct application of citronella oil has been found to raise the heart rate of some people.Health Canada is in the process of phasing out citronella entirely, as an insect repellent. The EPA, on the other hand, finds no known toxicity for citronella.
The market for natural citronella oil has been eroded by chemicals synthesised from turpentine derived from conifers. However, natural citronella oil and its derivatives are preferred by the perfume industry.
Use as an insect repellent
Video tracking of a stable fly, demonstrating repellency of citronella oil 
Citronella oil is popular as a 'natural' insect repellent. Its mosquito repellent qualities have been verified by research, including effectiveness in repelling Aedes aegypti (dengue fever mosquito). To be continually effective most citronella repellent formulas need to be reapplied to the skin every 30–60 minutes.
The US Environmental Protection Agency states that citronella oil has little or no toxicity when used as a topical insect repellent, with no reports of adverse effects of concern over a 60 year period. Because some products are applied to human skin, EPA requires proper precautionary labeling to help assure safe use. If used according to label instructions in the US, citronella is not expected to pose health risks to people, including children and other sensitive populations. The US Food & Drug Administration considers citronella oil as generally recognized as safe (GRAS).
Canadian regulatory concerns with citronella as an insect repellent are primarily based on data-gaps in toxicology, not on incidents.
In Europe, Ceylon type citronella oil is placed on the category 3 list, with some safety concern regarding methyl eugenol. In the UK, E.U. legislation governing insect repellents came into force in September 2006, which banned citronella as an active ingredient in any insect repellent products. This applied to both insect repellent for humans and animals. It can still be sold as a perfume, but must not be sold as an insect repeller.
^Nakahara, Kazuhiko; Alzoreky, Najeeb S.; Yoshihashi, Tadashi; Nguyen, Huong T. T.; Trakoontivakorn, Gassinee (October 2003). "Chemical Composition and Antifungal Activity of Essential Oil from Cymbopogon nardus (Citronella Grass)". Japan International Research Center for Agricultural Sciences37 (4): 249–52. INIST:15524982.
^Pattnaik, S; Subramanyam, VR; Kole, C (1996). "Antibacterial and antifungal activity of ten essential oils in vitro". Microbios86 (349): 237–46. PMID8893526. INIST:3245986.
^Mumcuoglu, Kosta Y.; Galun, Rachel; Bach, Uri; Miller, Jacqueline; Magdassi, Shlomo (1996). "Repellency of essential oils and their components to the human body louse, Pediculus humanus humanus". Entomologia Experimentalis et Applicata78 (3): 309–14. doi:10.1111/j.1570-7458.1996.tb00795.x.