First things first: If you're looking for a science-backed method of repelling mosquitoes, you don't need to shy away from synthetic repellents such as DEET and picaridin. DEET in particular has been widely used for decades, and studies show it protects against mosquitoes and ticks carrying malaria, West Nile virus, Zika virus, and Lyme, according to the Environmental Protection Agency. (Here's a list of the best DEET and picaridin mosquito repellents that are recommended by experts.)
Oil of lemon eucalyptus extract or PMD is a plant-based ingredient that has been proven to prevent mosquito bites. Here's what you need to know about PMD, plus the best mosquito repellents that contain the ingredient.
In a previous interview with Health, Rodriguez, who has extensively researched different types of repellents, said she would "strongly suggest" using a spray-on formula, such as those that contain DEET and picaridin, instead of wearable repellents.
If you do choose a natural alternative, though, there is one plant-based repellent that has been deemed effective in studies: oil of lemon eucalyptus extract.
What is oil of lemon eucalyptus extract?
Oil of lemon eucalyptus extract (also known as p-menthane-3,8-diol, or PMD) is derived from the leaves of lemon eucalyptus trees and chemically synthesized, usually in the form of a spray.
The ingredient has earned its mosquito-repelling stripes in two NMSU studies led by Rodriguez. In the first, published in the Journal of Insect Science in 2015, researchers looked at eight commercially available repellents, two fragrances, and a vitamin B patch, and noted whether each formula repelled or attracted disease-carrying mosquitoes Aedes albopictus and Aedes aegypti when applied to participants' hands. What they found: Cutter Lemon Eucalyptus Insect Repellent ($9; amazon.com), a plant-based spray that contains oil of lemon eucalyptus, was the only DEET-free formula to deliver strong and long-lasting results.
The second study, published in the Journal of Insect Science in 2017, looked at how effectively wearable repellents (such as the bracelets mentioned above) along with DEET and PMD sprays protect against female Ae. aegypti mosquitoes, the species most likely to spread Zika. Once more, the Cutter Lemon Eucalyptus Insect Repellent was found to be effective.
Animal studies on oil of lemon eucalyptus extract have not identified any adverse effects, although the FDA warns against using it on children under age 3, since it can irritate the eyes. Also important: The ingredient has not yet been studied for its ability to repel mosquitoes that carry diseases other than Zika, and unlike DEET, PMD repellents are not recommended for protection from ticks.
Where to buy it
Mosquito repellents that contain oil of lemon eucalyptus extract are relatively affordable and can be purchased online, but make sure you read the labels carefully: Oil of lemon eucalyptus extract is not the same as lemon eucalyptus essential oil. Somewhat confusingly, the latter is often marketed as being a mosquito repellent as well, but offers a much shorter window of protection (one hour versus up to six for oil of lemon eucalyptus extract).
Look for a product that lists "oil of lemon eucalyptus" as the active ingredient, like Cutter Lemon Eucalyptus Insect Repellent, the brand that was observed in the two Journal of Insect Science studies, and Repel Lemon Eucalyptus Natural Insect Repellent ($7 for 4 oz.; amazon.com). Both can deliver up to six hours of protection, but make sure to reapply after that.