Mosquitoes are one annoying sign of summer that can wreck an evening's dinner on the patio or an entire vacation: These pesky bugs not only leave itchy welts, but they can also transmit harmful diseases like West Nile virus, which is proving fatal in certain parts of the country, and dengue fever—the latter of which is now found in 28 states.
Before you reach for a can of insect repellent, however, you might want to read the ingredients panel. DEET, the most commonly used active ingredient in mosquito repellents, comes with some disturbing health problems, such as skin blisters, and it's been linked to birth defects and neurological damage. DEET can also interact adversely with permethrin, an ingredient common in bug-repellent clothing, by enhancing your body's ability to absorb permethrin, a synthetic insecticide linked to headaches, memory loss, and muscle and joint pain.
To add insult to injury, a study published in the Proceedings of the National Academy of Sciences found that mosquitoes are growing resistant to DEET. The researchers noted that female mosquitoes belonging to the species that carries yellow and dengue fevers were not deterred by DEET when the chemical was sprayed on the arms of human volunteers, and that the mosquitoes passed that DEET-resistant trait to their offspring. Fortunately, there are safer insect repellents that are just as effective, if not more so, than DEET.
Here are a few ingredients recommended by the U.S. Centers for Disease Control and Prevention (CDC), as well as some natural oils that have been tested by scientists (look for any of these ingredients listed on the "Active Ingredients" panel when shopping for insect repellent):
• Picaridin. A chemical derived from pepper, picaridin (which may be listed on products as KBR 3023 or by its chemical name, 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester) has shown the most promise as being an effective DEET replacement without any health affects. A study published in the 2004 issue of the journal Tropical Medicine & International Health found that picaridin was more effective at repelling the yellow- and dengue-fever-spreading mosquitoes than DEET, making it a suitable alternative if your summer vacation takes you to a tropical locale where those diseases are common.
• Oil of lemon eucalyptus. The only plant-based repellent recommended by the CDC, oil of lemon eucalyptus has also been found effective against disease-carrying mosquitoes. It hasn't been tested against those that carry tropical diseases, but a 2004 study in the Journal of Medical Entomology found that products containing 26 percent oil of lemon eucalyptus protected against West Nile virus-carrying mosquitoes for about three hours longer than products containing 7 percent DEET. Look for products carrying at least 26 percent oil of lemon eucalyptus, which may also be listed as para-Menthane-3,8-diol, but not pure oil of lemon eucalyptus. The undiluted essential oil hasn't been found as protective against bugs as it is when added to other product formulations.
• IR3535. It sounds more like a tax code than an insect repellent, but this ingredient was found in the Journal of Medical Entomology to be as effective as DEET against West Nile–carrying bloodsuckers. It's a synthetic version of amino acids found in vitamin B, and has been used for decades in Europe with no reported adverse side effects.
• Other plant-based repellents. In addition to IR3535 and oil of lemon eucalyptus, the Journal of Medical Entomology study looked at products containing soybean oil, citronella, neem oil, and geraniol (the oil found in geraniums). All were effective against mosquitoes for up to three hours, but soybean oil was found to be the most effective of the four. It worked for more than seven hours, as long as products containing 15 percent DEET, picaridin, oil of lemon eucalyptus, and IR3535. Geraniol was next in line, warding off bugs for up to five hours, as long as products containing 7 percent DEET. Citronella and neem oil worked for just three hours before needing to be reapplied.
Terminix AllClear also makes a handy portable LED lantern with a programmable all-natural mister that repels mosquitoes within a 300 square-foot outdoor area using geraniol, not toxic pesticides.