A mosquito repellent from tomatoes--the alternative to DEET? (EH Update).

Dr. Michael Roe of North Carolina State University has discovered that a substance produced by tomatoes repels mosquitoes and other insects more effectively than DEET-and is safer.

DEET (N, N-diethyl-meta-toluamide) was developed by the U.S. Department of Agriculture for the Army in 1946. While the U.S. Environmental Protection Agency (U.S. EPA) has found that the normal use of DEET does not present a health concern to the general population, the use of products containing DEET has been associated with rashes, swelling, itching, eye irritation, and, less frequently, slurred speech, confusion, and seizures. Products with high concentrations of DEET are considered particularly hazardous to children, and U.S. EPA no longer allows the label of a product containing DEET to claim that the product is safe for children. Recent research at Duke University with rats showed that frequent and prolonged use of DEET caused brain-cell death and behavioral changes in the animals.

Roe discovered the insect-repellent capacity of tomatoes by accident. "I was listening to a scientific presentation about protein mimics as a diet pill for the control of mosquito larvae," he said. He realized that the compounds being discussed were similar to a compound found in wild tomatoes. Years earlier, he and another scientist had studied the compound, which apparently is part of the tomato's natural defenses against insects, to see if it might be used to control worms that eat tomatoes.

Roe revisited the compound and tested it as a mosquito repellent. He found that it repelled not only mosquitoes, but also ticks, fleas, cockroaches, ants, and biting flies, as well as agricultural pests such as aphids and thrips.

The compound is already used to make cosmetics, so its toxicity has been studied. "What this means is that the toxicology has been done, which is a big step toward commercialization," Roe said. "It's found in tomatoes, it's natural, it can be obtained organically, it's safe, and it's at least as effective as DEET, all features that the public would want for a new-generation insect repellent."

With concern rising about West Nile virus and Lyme disease, the discovery of the new insect repellent is timely. The university has licensed the right to produce the substance as an insect repellent to Insect Biotechnology, Inc., a Durham company that specializes in developing and marketing biochemical insecticides. The cost of producing the repellent is expected to be competitive with the production costs of DEET. Insect Biotechnology has applied to U.S. EPA for approval of the insect repellent for use in several products and hopes that the new product, called IBI-246, will win approval by the end of the year. On the scale used by U.S. EPA to gauge toxicity, IBI-246 is considered slightly safer than DEET.