DEET (short for N,N-diethyl-meta-toluamide) is the most widely used insect repellent in the world for a very good reason – it works really, really well! Just a quick spray on exposed skin keeps mosquitoes, flies, fleas, chiggers, and ticks away. Developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, millions of people worldwide use DEET to ward off vector-borne diseases. First of all, why would researchers study DEET if it works so well? While DEET is an effective repellent, it doesn’t work against all bugs, it’s corrosive to plastics and there are concerns about its effect on human health.

Structural Formula for N, N-diethyl-meta-toluamide (DEET).

Courtesy of Wikipedia - Click on the image for a larger version.

How DEET actually works has puzzled scientists for more than 50 years. Scientists long surmised that DEET masks the smell of the host, or jams or corrupts the insect’s senses, interfering with its ability to locate a host. Mosquitoes and other blood-feeding insects find their hosts by body heat, skin odors, carbon dioxide (breath), or visual stimuli.

Amazingly, within a few months this year, scientists from two different labs have come up with competing explanations of how DEET works. In March of 2008, researchers at Rockefeller University in New York, said that DEET jams odorant receptors in insect nervous systems, in effect masking odors that would ordinarily attract the bugs. According to Dr. Leslie B. Vosshall, a researcher who worked on the project, now that they know that DEET targets OR83b co-receptors, they can quickly screen thousands of other compounds in hope of finding one that is even more effective and has fewer disadvantages.

Are you sure, ask researchers at the University of California, Davis? Mosquitoes flee because of their intense dislike for the smell of the chemical repellent and not because DEET jams their sense of smell. In August 2008, in a paper published in The Proceedings of the National Academy of Sciences, they provide a simpler explanation. Mosquitoes, they say, smell DEET directly and avoid it.

Dr. Vosshall, involved in the earlier study, said that her team stood by its work, and that its findings were based on a variety of experiments. So for now, the jury is still out.

Connecting to the National Science Education Standards

These competing explanations on how DEET works provides a perfect example of one aspect of the nature of science – Scientific Claims are Subject to Peer Review and Replication. Researchers in labs across the world work on answering many of the same questions. The results of their work are published in peer reviewed journals so that researchers around the world can examine their data and logic, identify alternative explanations, and replicate observations and experiments. Peer review is an integral part of genuine scientific enterprise and goes on continuously in all areas of science.

The National Science Education Standards in the History and Nature of Science Content Standard G describes what middle school students should understand about this part of the nature of science, including:

It is normal for scientists to differ with one another about the interpretation of the evidence or theory being considered.

Different scientists might publish conflicting experimental results or might draw different conclusions from the same data.

It is part of scientific inquiry to evaluate the results of scientific investigations, experiments, observations, theoretical models, and the explanations proposed by other scientists.

Although scientists may disagree about explanations of phenomena, about interpretations of data, or about the value of rival theories, they do agree that questioning, response to criticism, and open communication are integral to the process of science.

Additional Resources

Read the entire National Science Education Standards online for free or register to download the free PDF. The content standards are found in Chapter 6.

Science For All Americans Online: The Nature of Science

Science for All Americans consists of a set of recommendations on what understandings and ways of thinking are essential for all citizens in a world shaped by science and technology.

Household Product Database

List of products that contain DEET.

Chemical Technical Summary for Public Health and Public Safety Professionals

The Department of Health and Human Services provides a summary of all medical cases and research done on DEET.

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