Citronella oil is obtained from the leaves and stems of different species of Cymbopogon, better known as lemongrass. It is not to be confused with Citriodiol®. Citronella oil is used extensively in perfumes, cosmetics, candles and flavouring industries. It is also found in insect repellents, but perhaps more from its familiarity rather than its efficacy, and studies have shown that caution should be taken. It is true that the oil has repellent properties, but it is the length of time the protection lasts that causes concern. Citronella oil is very volatile, meaning that it evaporates very quickly off the skin so that insect repellents with this oil as the active substance need to be reapplied every 20-60 minutes, depending on the formulation and the concentration of Citronella oil.
Apart from the source of the oil, the biggest difference between Citronella oil and Citriodiol® is that Citriodiol® contains at least 64% of the naturally occurring constituent PMD (p-menthane-3,8-diol). Citronella oil, however, only contains trace quantities of PMD. This is an important distinction because PMD is the constituent primarily responsible for the efficacy of Citriodiol® in repelling biting insects and other arthropods. In side-by-side independent comparisons, Citriodiol® products repel biting insects, such as mosquitoes, 4 to 8 times longer than citronella oil products (Barnard 2004).
Citronella can be sold as a plant-based insect repellent in the United States but efficacy claims are very limited. However, in a more recent decision, citronella is not being supported as an insect repellent active substance in Europe under the EU BPR, and has not been able to be sold as an insect repellent product within the EU since 2006.
In addition, the Canadian PMRA is currently considering a ban on Citronella based repellent products due to a lack of safety data and concerns surrounding some of the oils components.