Jerusalem, 24 February, 2026 (TPS-IL) — A mystery that has lingered for thousands of years — why certain plant extracts reliably drive mosquitoes away — has now been solved by an international team of scientists led from Israel. The findings explain how compounds from camphor trees trigger a hard-wired avoidance response in mosquitoes, offering a potential blueprint for a new generation of more precise and safer repellents.
For millennia, people across Asia and beyond have relied on camphor- and borneol-rich plant materials to keep mosquitoes at bay, even though the insects are strongly attracted to human cues such as carbon dioxide and body odors. Until now, scientists did not fully understand how repellent odors could override those attraction signals inside the mosquito brain.
A study led by Dr. Jonathan Bohbot of the Department of Entomology at the Hebrew University of Jerusalem identifies a specific odorant receptor in mosquitoes that detects borneol, a natural compound found in camphor tree oils that have been used for centuries as insect repellents.
The team of researchers from Baylor University, the University of Washington, the University of California, the Swedish University of Agricultural Sciences, and other international partners discovered that a highly conserved odorant receptor, known as OR49, is finely tuned to detect borneol in several major mosquito species, including those responsible for spreading dengue, Zika, and West Nile virus. Activation of this receptor triggers a dedicated neural pathway that causes mosquitoes to actively avoid the source of the odor.
Using a combination of genetic engineering, electrophysiological recordings, brain imaging, and behavioral experiments, the team showed that borneol activates a specialized sensory neuron located in the mosquito’s maxillary palp, an organ central to host detection. Notably, this neuron sits directly beside attraction-sensing neurons that help mosquitoes locate humans, revealing a built-in neural architecture that integrates repulsion signals alongside host-seeking cues.
To accelerate the identification of relevant natural activators of this pathway, the researchers turned to an unexpected source: cannabis essential oil. By screening and fractionating multiple cannabis oil preparations and using OR49 activation as a biological readout, they were able to isolate borneol as the most potent activator of the receptor. The approach allowed the team to link complex plant mixtures to specific behaviorally active compounds and connect traditional botanical remedies to precise mosquito sensory targets.
Behavioral tests confirmed the real-world significance of the findings. Mosquitoes exposed to borneol were significantly less likely to approach human skin and spent far less time nearby. When the OR49 receptor was genetically disabled, mosquitoes no longer responded to borneol, demonstrating that this single receptor is essential for the repellent effect.
“These results explain, at a molecular and neural level, why borneol has been used as a mosquito repellent for thousands of years,” said Bohbot. “By pinpointing the exact receptor involved, we can begin to design more targeted and potentially safer repellents that exploit the mosquito’s own sensory system.”
The findings pave the way for a new generation of mosquito repellents that work by precisely activating the insect’s own avoidance circuitry rather than relying on broad chemical irritation. By targeting the OR49 receptor directly, future repellents could be effective at lower concentrations, provide longer-lasting protection, and perform more consistently across different mosquito species. This approach also opens the door to alternatives to more widely used but potentially harmful chemicals such as DEET.
Beyond consumer products, the research has important implications for public health and disease prevention. More effective repellents could help limit the spread of diseases such as dengue, Zika, malaria, and West Nile virus, especially in high-risk regions. The findings also support the development of spatial repellents, including treated clothing, bed nets, indoor diffusers, and outdoor barriers, offering continuous protection in homes and public spaces rather than relying solely on skin-applied solutions.
The study was published in the peer-reviewed Nature Communications.
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