New Study Shows Bug Spray Could Be Having An Unexpected Effect On Mosquitoes

While mosquitoes seem like mindless, simple creatures, they may be a little smarter and savvier than previously thought. One of the biggest tips for keeping mosquitoes away is to wear an effective bug spray repellent, but a study published in May 2026 suggested they can associate the common ingredients of these products with a tasty meal. The study, appearing in the Journal of Experimental Biology, lab tested how Aedes aegypti mosquitoes responded to DEET exposure during feeding on blood and sugar. Aedes aegypti, also called the yellow fever mosquito, is an invasive species common to the southern United States and known to bite aggressively and transmit disease. Surprisingly, the studied insects were seemingly able to remember that the presence of DEET indicated delicious blood was nearby. While this does not mean that bug sprays containing DEET don't work, it does reveal something about how mosquitoes respond to repellents.

Using an insect repellent containing DEET is one of the most effective methods for preventing mosquito bites and has been thought to work by warding off mosquitoes with a fragrance they can't tolerate. Professor Claudio Lazzari with University of Tours, France, one of the authors of the current study, discussed with The Guardian how these pests responded differently to repellents than expected. "For a long time, it was believed that repellants worked solely because of their chemical properties, either by being toxic or unpleasant to mosquitoes and driving them away, or by blocking their ability to detect humans," Lazzari explained. "However, our findings suggest that the reaction can be modified by experience." 

This study does not speak to the effectiveness of DEET but rather to a mosquito's ability to learn and adapt to repellents. Per The Guardian, 60% of the lab mosquitoes that were conditioned to associate DEET with blood showed a biting response when they smelled the chemical, even if there was no blood nearby. The insects' responses showed that they can remember that DEET smell is connected with blood, and they can learn not to avoid the chemical when they would have before.

Because this study was conducted in a controlled environment with a specific type of mosquito, the pests will likely behave differently in nature amidst a range of variables. However, these findings suggest that consistently applying bug spray could be vital to using DEET repellents effectively. Clément Vinauger, a co-author on the study and associate professor at Virginia Tech, explained the everyday implications of the findings to Virginia Tech News. "If someone applies DEET and the concentration fades over time, but a mosquito still manages to feed, the insect may begin associating that smell with a reward," said Vinauger. "That's a possibility we should take seriously when we think about how repellents are used in the real world." Though you can try DIY bug sprays and repellents, DEET still offers vital protection as long as you reapply it. Vinauger suggested that frequently reapplying bug spray will likely offer better protection than spraying a lot at one time.