New non-toxic mosquito repellent uses skin bacteria and L-(t)-lactic acid to protect for up to 11 days

The most striking point is that it contains no toxic substances.

Mosquitoes-formidable carriers of diseases such as dengue, malaria and the Zika virus-have long been a major global public health concern. Each year, this pest is responsible for the deaths of around 1 million people worldwide, placing it at the top of the list of the most dangerous animals.

While conventional protection methods, including DEET (N,N-diethyl-3-methylbenzamide, a repellent in use since the 1950s), can offer decent protection, they also come with drawbacks, particularly around toxicity.

Now, a team of researchers has created a novel repellent that harnesses bacteria naturally found on the human epidermis to provide long-lasting protection against mosquito bites. Their findings were published in PNAS Nexus.

Lactic acid: an unexpected ally against mosquitoes

This approach stems from a detailed understanding of how female mosquitoes are attracted to humans.

Why female mosquitoes are drawn to us

Female mosquitoes respond strongly to several cues, including body heat, exhaled carbon dioxide and the airborne chemicals produced by the human skin microbiome.

Reducing attraction by altering L-(t)-lactic acid production

Among these scent compounds, L-(t)-lactic acid turned out to be a powerful attractant. However, the researchers found that by modifying the bacteria responsible for producing this acid, it becomes possible to sharply reduce how appealing a person is to mosquitoes.

When these genetically modified bacteria were applied to the skin, the results were dramatic. Just three days after application, the team observed a 64.4% reduction in mosquito attraction. Even more notably, this protection can last up to 11 days, far exceeding the effective window of traditional repellents.

A non-toxic alternative to traditional repellents

A key feature of this scientific advance is its strong safety profile. Unlike DEET-whose use raises concerns about potentially harmful effects on wildlife and humans-the genetically modified micro-organisms used in this repellent currently show no known health risk.

Why non-toxicity matters for biodiversity

This is especially significant in regions where heavy reliance on chemical substances has damaging impacts on local biodiversity.

The researchers behind the work hope this breakthrough will encourage wider adoption of biotechnological solutions for pest control. For managing insects that transmit disease, it could represent a genuine turning point.