The active compound behind this botanical shield is nepetalactone, a bicyclic monoterpenoid that constitutes the major volatile component of catnip essential oil. Long known as the chemical that sends domestic cats into paroxysms of euphoria, nepetalactone binds to specific olfactory receptors in insects, triggering a powerful avoidance response. Its mechanism, while not identical to that of DEET, achieves a similar outcome: mosquitoes fail to home in on the carbon dioxide, lactic acid, and other skin emanations that normally guide them to a human host. Yet despite its known efficacy, nepetalactone has languished in scientific obscurity because natural compounds cannot be patented, offering little financial incentive for pharmaceutical companies to invest in formulation and distribution.

That economic void became the starting point for the Cardiff-Uganda collaboration. “There is a real need to reduce the reliance on malaria medicines because malaria can develop resistance to drugs,” explains Dr Simon Scofield, a senior lecturer at Cardiff University. “Mosquito repellents represent one of the primary measures used to reduce the risk of malaria by reducing mosquito landing and biting events.” The team realized that an ideal solution would meet two criteria simultaneously: it had to be highly efficacious against Anopheles vectors, and it had to be manufacturable within the economic reach of subsistence farmers who earn a few dollars a day. Imported DEET products, while effective, fail on the second count. Instead, the researchers turned to catnip, a hardy perennial that thrives in Ugandan soils, requires minimal agricultural inputs, and yields an essential oil rich in nepetalactone that can be extracted using simple steam distillation equipment.

To transform crude oil into a usable product, the scientists formulated DSK Lotion—named in honor of Dison Stephen Kalebo, a local community leader instrumental in the project. The lotion stabilizes nepetalactone in an emulsified base that is both skin-friendly and long-lasting. Crucially, the team subjected this formulation to rigorous double-pronged testing. In laboratory experiments, they deployed a Y-tube olfactometer, a standard apparatus in chemical ecology in which hungry female Aedes aegypti mosquitoes are released at the base of a Y-shaped tube and allowed to choose between two airstreams—one passing over untreated human skin and another over skin treated with the repellent. The proportion of mosquitoes that oriented toward each arm provides a quantitative measure of repellency. The results were striking: a 6% nepetalactone formulation repelled mosquitoes as effectively as a commercial 20% DEET preparation, and even a 2% formulation retained most of that protective power.

To confirm these findings under real-world conditions, the team conducted field trials using the human landing catch assay, a method in which trained collectors sit with exposed lower limbs and aspirate any mosquito that attempts to land. This gold-standard entomological technique, though labor-intensive, provides the most ecologically relevant data on host-seeking behavior. In the Budaka district of eastern Uganda, where malaria transmission is perennial, the 6% nepetalactone lotion reduced mosquito landings to statistically indistinguishable levels from DEET, while the 2% formulation offered only a modest reduction in protection. Importantly, no adverse skin reactions were reported, and users consistently rated the lotion’s herbal, slightly minty scent as far more pleasant than the chemical odor of DEET.

Beyond its sensory appeal, the catnip lotion carries profound economic implications. Because the entire production chain—from planting and weeding to oil extraction and lotion manufacture—is carried out by local workers employed by the community organization CEMPOP Uganda Limited (Community Enterprise Model for Plant Oil Production), the money stays within the region. Grant funding has so far allowed the lotion to be distributed free of charge during trials, but the next phase involves selling it at a nominal price, creating a circular economy in which growers, processors, and distributors all earn a livelihood while furnishing their neighbors with an essential public-health tool. “Once we know that we can sell and distribute the repellent at a low-cost, that should generate a self-sustaining system where the money is flowing back to everybody at each stage in the development,” says Scofield.

The broader ecological versatility of nepetalactone further strengthens the case for scale-up. In addition to Anopheles mosquitoes, the lotion shows promise against other disease-spreading arthropods, including midges that transmit bluetongue virus in livestock and ticks responsible for Lyme borreliosis. This opens the door not only to agricultural applications but also to markets in the global north, where consumer demand for plant-based insect repellents is rising rapidly. Regulatory pathways will need to be navigated, but the fact that catnip oil is already listed as a food-flavoring agent by the European Food Safety Authority should smooth the toxicological approval process.

Looking ahead, the team envisions replicating the CEMPOP model across other malaria-endemic countries, adapting it to local plant species and cultural contexts. The project thus stands as a compelling example of how rigorous biological science, when integrated with social entrepreneurship, can bypass the shortcomings of market-driven pharmaceutical development. It demonstrates that a neglected botanical molecule, given the right interdisciplinary push, can become a frontline weapon against one of humanity’s oldest microbial foes. As climate change expands the range of mosquito vectors, such frugal, community-led innovations may soon prove indispensable.

Subject of Research: Development and field validation of a catnip oil-based mosquito repellent lotion for malaria prevention
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Image Credits: Credit: Cardiff University and CEMPOP