Look for plant-based repellents; stick with low-dose DEET if it’s absolutely necessary.

Armed resistance: Protect yourself from bugs, but look for DEET-free options.

RODALE NEWS, EMMAUS, PA—Invented in the 1950s, DEET (N,N-diethyl-m-toluamide) is considered one of the most effective mosquito repellents on the market, and billions of people have used it over the past 45 years. However, occasional reports of death (from ingestion), asthma attacks, and seizures related to DEET application have consumer-advocacy groups questioning its safety. Now a study published in the British journal BMC Biology suggests that it could interfere with your nervous system.

THE DETAILS: The researchers used animals and computer modeling to study the effects of DEET on the central nervous system. They found that DEET inhibits activity of the enzyme cholinesterase, which is vital to proper functioning of the nervous system.

WHAT IT MEANS: Aside from possibly damaging your nerves, using DEET can also cause severe skin irritation, blistering, and burning in some individuals. It may be particularly dangerous when used in combination with other pesticides. In one animal study, DEET was found to cause behavioral problems when combined with the insect repellent permethrin, which is added to some brands of outdoor clothing to keep bugs away. Plus, being a potent synthetic chemical, DEET builds up in rivers and streams. A U.S. Geological Survey sampling of stream water quality detected DEET in 73 percent of sampled waterways, some of which may feed into drinking-water supplies.

Most international health organizations, including the U.S. Centers for Disease Control and Prevention (CDC), recommend using DEET when traveling to areas where mosquito-borne diseases like malaria pose a serious threat. However, the CDC has also tested a variety of other plant-based repellents on varieties of mosquitoes found in the U.S. and found them to be just as effective as DEET—and not surrounded by a fog of uncertainty regarding health effects.