Study: A herb that is giving mosquito repellents a run for their Money

Catnip could provide a low-cost alternative to DEET for repelling mosquitoes, researchers say. [iStockphoto]

A lotion made from catnip could offer an affordable, locally produced alternative to one of the world's most widely used mosquito repellents after researchers found it was just as effective as DEET in field trials.

Catnip is a herb from the mint family best known for making many cats playful, but it also contains a natural substance that mosquitoes dislike, making it a promising plant-based alternative to traditional insect repellents.

DEET is the active ingredient in many of the world's leading mosquito repellents and has been considered the gold standard for keeping mosquitoes and other biting insects away for decades because of its proven effectiveness.

Beyond preventing mosquito bites, repellents help protect against several diseases spread by mosquitoes.

In Kenya, mosquitoes transmit malaria as well as viral diseases such as dengue fever, chikungunya, yellow fever and Rift Valley fever.

Although these illnesses are spread by different mosquito species, health experts say reducing mosquito bites remains one of the most effective ways to lower the risk of infection.

The findings, presented this week at the Society for Experimental Biology annual conference in Florence, Italy and published in the journal Scientific Reports, come at a time when malaria continues to be one of the world's deadliest mosquito-borne diseases.

Keep Reading

According to the World Health Organisation's latest World Malaria Report 2025, there were an estimated 282 million malaria cases and about 610,000 deaths worldwide in 2024.

The African Region accounted for about 94 per cent of all malaria cases and 95 per cent of malaria deaths, with children under five bearing the greatest burden.

Kenya remains among the countries with a high malaria burden.

The disease is endemic in counties around Lake Victoria and the Coastal parts of Kenya. Kenya registers approximately 4 million malaria cases annually searching for affordable mosquito prevention tools especially important.

Researchers from Uganda and Wales tested lotions made from catnip (Nepeta cataria), a plant more commonly associated with its playful effect on cats than its medicinal value. The herb contains a natural compound that has long been known to repel insects.

In field trials in eastern Uganda, volunteers applied either a lotion containing 2 per cent catnip oil, 6 per cent catnip oil, a commercial lotion containing 15 per cent DEET, or a placebo cream before exposing their legs to mosquitoes during evening biting hours.

Both catnip formulations significantly reduced mosquito landings compared with the placebo. Most notably, the 6 per cent catnip lotion performed just as well as the commercial 15 per cent DEET repellent, while the 2 per cent formulation was only slightly less effective.

Simon Scofield, a senior lecturer at Cardiff University, said affordability was one of the key reasons behind the project.

"We found that a 6% catnip oil was just as effective as DEET, and the 2% catnip oil was only marginally less effective than that."

Commercial repellents remain beyond the reach of many rural households, he said.

"DEET is out of the price bracket for most rural Ugandan subsistence farmers, so buying commercially available mosquito repellents is just not practicable. We wanted to make a repellent which is highly efficacious, but also allows local people to be involved in the production cycle so that it costs a minimal amount of money."

According to the study, the catnip oil used in the lotion contained high levels of a natural substance that mosquitoes avoid. Researchers found that a single application protected throughout the four-hour evening period when mosquito biting is usually at its highest in rural communities.

Beyond its effectiveness, scientists say the innovation could also boost local economies. Instead of relying on imported repellents, catnip can be grown locally, processed into oil and manufactured into lotion through community-based enterprises. While production is currently supported by grant funding, researchers hope commercial manufacturing will eventually create a self-sustaining supply chain that benefits farmers and local businesses.

The findings build on laboratory research published in 2024, which showed that catnip oil concentrations as low as two per cent repelled more than 70 per cent of Aedes aegypti mosquitoes for up to four hours. The latest study demonstrates similar protection under real-world conditions.

Experts, however, caution that skin-applied repellents should complement, not replace, existing malaria control measures.

Swai Kyeba, a research entomologist at the Ifakara Health Institute in Tanzania who was not involved in the study, welcomed the findings but urged caution before large-scale adoption.

"New vector-control tools are necessary in the fight against malaria, especially those that are cheap and locally produced, to help improve accessibility."

He noted that repellents applied to the skin must be used consistently and should be used alongside proven interventions such as insecticide-treated mosquito nets and indoor residual spraying.

"A challenge with topical repellents is low compliance because they require regular application. This is why they remain a complementary tool in the fight against malaria."