How DEET Works

DEET is available to the consumer in various forms. In fact, the­ U.S. Environmental Protection Agency currently registers 39 companies with about 140 products containing DEET [source: EPA]. DEET products are available as liquids, lotions, sprays, and impregnated materials like wristbands or wipes. These products are all for direct application to the skin.

So how much DEET do you need to rub onto your skin to make yourself unattractive or invisible to biting insects? Currently, DEET skin application products are available in concentrations from four to 100 percent [source: EPA]. A higher concentration of DEET doesn't mean it's more effective -- it just means it lasts longer. The more DEET a product contains, the longer it will protect you from insects. For example, if you plan to do some gardening in the yard for only an hour or so, a product with 5 to 7 percent DEET should be enough. For a longer, more intense outdoor experience like fishing or hiking, 25 to 30 percent is a better choice [source: SE Johnson].

That said, the Centers for Disease Control and Prevention (CDC) states that any concentration more than 50 percent doesn't offer any added protection [source: CDC]. In fact, Canada limits all consumer DEET products to a concentration of 30 percent or less [source: Health Canada]. If you need longer protection, labels recommend that you simply reapply once the repellent stops working.

The EPA doesn't restrict DEET concentration for children, saying there's no data to suggest any negative effects [source: EPA]. However, the American Academy of Pediatrics recommends using DEET products only on children older than two months and to keep it away from their hands, eyes and mouths [source: AAP].

Many people do feel DEET is dangerous and opt not to use it on themselves or their children. We'll look at DEET side effects and controversies on the next page.