Plant-based repellents have been used for generations in traditional practice as a personal protection measure against host-seeking mosquitoes. Knowledge on traditional repellent plants obtained through ethno botanical studies is a valuable resource for the development of new natural products. Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as “safe” in comparison to long-established synthetic repellents although this is sometimes a misconception. There is a need for further standardized studies in order to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety. This paper presents a summary of recent information on testing, efficacy and safety of plant-based repellents as well as promising new developments in the field.
Citronella
Essential oils and extracts belonging to plants in the citronella genus (Poaceae) are commonly used as ingredients of plant-based mosquito repellents (Table (Table1),1), mainlyCymbopogon nardus that is sold in Europe and North America in commercial preparations. Citronella has found its way into many commercial preparations through its familiarity, rather than its efficacy. Citronella was originally extracted for use in perfumery, and its name derives from the French citronelle around 1858 [28]. It was used by the Indian Army to repel mosquitoes at the beginning of the 20thcentury [29] and was then registered for commercial use in the USA in 1948 [30]. Today, citronella is one of the most widely used natural repellents on the market, used at concentrations of 5-10%. This is lower than most other commercial repellents but higher concentrations can cause skin sensitivity. However, there are relatively few studies that have been carried out to determine the efficacy of essential oils from citronella as arthropod repellents. Citronella-based repellents