DEET Doesn't Actually Repel Insects, So What Does It Do?

Recent studies have shown that an insect repellent called DEET not only keeps insects away but does so by confusing their sense of smell. The repellent temporarily messes up the brain work of insects, leading to confusion in the odor receptors of an organism. As a result, insects don’t even go around their favorite smells if DEET is present.

DEET was developed in 1940 and today, most insect repellents contain the product. Though DEET works on insects like spiders and ticks, C. elegans, a species of worm, also show effects from the repellent according to recent tests. However, the product doesn’t repel every organism.

Intrigued by how DEET might affect different organisms, three scientists – Emily Dennis, a former graduate, Leslie Vosshall, Rockefeller’s Robin Chemers Neustein Professor, and Cori Bargmann, Rockefeller’s Torsten N. Wiesel Professor – started an experiment on the product.

In their experiment, they tested how DEET impacts the actions of C. elegan, an organism which has a strong sense of smell. Initially, when the worms were individually placed with DEET, evidence showed that they didn’t purposely act to avoid the repellent. This data suggested that DEET doesn’t simply scare away every organism that approached it.

Following the initial observation, DEET was then mixed into agar, a gel-like substance used as a surface for the worms to crawl on in a petri dish. Researchers observed that the incorporation of DEET into the gel surface led to constricted movements performed by the worms. For example, the worms didn’t move toward isoamyl alcohol, a product they usually attract to. Additionally, the worms began to interact more with 2-nonanone, which is a substance they usually avoid. These observations concluded that DEET can interfere with an organism’s responsiveness to typical “good” and “bad” smells, but not shut down the organism’s ability to smell completely.

Furthering their studies, the researchers discovered that the worm’s sensitivity to DEET depended on the gene str-217, which are present in neurons called ADL cells. After activating these cells, the worms were observed to have paused in their positions. These behaviors were replicated in the earlier experimentation with DEET incorporation into agar. Overall, these data points indicated that the DEET chemical functioned partly by activating neurons that induce pausing.

Vosshall says, “Somehow activating ADL puts the worms into a frame of mind where they’re more introspective, they’re pausing more, they’re not paying as much attention to odors. But if you take away the right gene or neuron, this spell is broken.”

These studies have shown that DEET is a chemical that affects all types of species. This substance that keeps unwanted organisms away is still being researched for better understanding.

“Something about DEET is really special. And I think we’re just starting to uncover all the ways that it can affect different neurons, receptors, and species,” adds Dennis.

[Sources: Rockefeller University; ScienceDaily]