French study: mosquitoes can develop conditioned reflex to repellents

A laboratory experiment by French scientists has revealed that mosquitoes may develop a conditioned reflex to repellents if these products are used incorrectly. The insects can begin to associate the repelling scent with a desirable food source, potentially reducing the effectiveness of the repellent over time.

A new study by French researchers has found that mosquitoes are capable of forming a conditioned reflex in response to insect repellents — a discovery with practical implications for the millions of people who rely on these products each summer.

In controlled laboratory experiments, scientists observed that when repellents were applied incorrectly or inconsistently, mosquitoes began to associate the deterrent scent with the presence of a food source — in other words, a human host. Over time, this association could cause the insects to become less deterred by the very products designed to keep them away.

The findings suggest that the manner in which repellents are applied matters significantly. Repeated exposure under conditions where the mosquito still manages to reach its host could, according to the research, gradually erode the protective effect of even well-established repellent compounds.

As warmer months approach and outdoor activity increases across Europe and beyond, the study serves as a timely reminder for consumers to follow usage instructions carefully. Scientists caution that improper or irregular use of repellents may inadvertently train mosquitoes to overcome their natural aversion to these chemicals.