Every year, approximately one-third of Americans use insect repellents containing the insecticide DEET. Duke University Medical Center pharmacologist Mohamed Abou-Donia has spent 30 years researching the effects of pesticides. He has found that prolonged exposure to DEET can impair functioning in parts of the brain."Damage to these areas could result in problems with muscle coordination, muscle weakness, walking or even memory and cognition."Abou-Donia says rats given even small doses of DEET for 60 days had a harder time accomplishing even the easiest tasks. Abou-Donia says short-term exposure to DEET does not appear to be harmful, but warns against using any product with more than a 30 percent concentration. Use as little of the product as you can, and don't use a product containing DEET if you're taking any medication."We found that the combined exposure to DEET and other chemicals is more dangerous than just DEET alone."Abou-Donia also warns to never put a product containing DEET on an infant's or child's skin. The side-effects could be even more serious. I'm Cabell Smith for MedMinute.