Study on DEET: Mosquitoes Can Associate Repellent With Blood Meals Under Laboratory Conditions

Tours – 20 July 2026: A current debate about mosquito sprays is based on a study by the Institute of Insect Biology at the University of Tours. The research team examined the active ingredient DEET, which is used in numerous repellents worldwide. In the laboratory, individual yellow fever mosquitoes of the species Aedes aegypti were able to learn to associate the previously deterrent smell with the prospect of a blood meal.

The results were published at the end of May in the Journal of Experimental Biology. For the experiment, mosquitoes were repeatedly exposed to a DEET scent while also being offered a blood stimulus. After this targeted conditioning, some animals reacted differently than before: the scent no longer had only a repellent effect, but could encourage their approach to a potential food source.

The researchers therefore describe a learning effect, not evidence that DEET sprays regularly make people more attractive to mosquitoes in everyday life. The experimental setup was highly controlled and relied on repeated pairings of the scent and a blood meal. Under normal conditions, mosquitoes encounter many changing smells, air movements, body heat and carbon dioxide, all of which influence their search.

Lead author Claudio Lazzari of the University of Tours has therefore warned against an exaggerated interpretation. In his assessment, it is highly unlikely that the mechanism observed in the laboratory would develop in the same way in typical everyday situations. Based on current evidence, DEET remains an effective active ingredient for reducing mosquito bites, particularly in areas with mosquito-borne diseases.

In France, the issue is particularly relevant this summer. Health authorities began enhanced surveillance of dengue, chikungunya and Zika on 1 May 2026. The tiger mosquito is now established across large parts of the country. Health protection therefore remains a combination of personal protection and the removal of small accumulations of water where larvae can develop.

Santé publique France recommends protecting exposed skin with a suitable repellent, wearing light-colored clothing that covers the body, and using insect screens on windows and doors. Water in plant saucers, buckets, gutters or open containers should be removed regularly. These measures reduce not only bites but also the number of potential breeding sites near homes.

The new study therefore primarily provides an indication of mosquitoes’ capacity for learning and the complexity of their sense of smell. It is not a reason to stop using proven repellents across the board. What remains crucial is correct use according to the manufacturer’s instructions and a protection strategy that combines repellents with clothing, nets and the avoidance of breeding sites.