Ask Dr. H: Does citronella chase away mosquitoes?

Question: With all the attention these days to West Nile virus, how safe and effective are citronella candles in dealing with mosquitoes?

Answer: Citronella is an oil distilled from the leaves of an Asian grass that's a close cousin of the lemongrass used in Thai cuisine. The word citronella means "lemonlike." When citronella is used in the usual 3 percent concentration in candles or the 5 percent concentration in incense, the oil burns and gives off a smoke that mosquitoes and other flying insects find rather noxious. It's not a poison to them, but an odor that they'd rather avoid. This time of year, you'll see lots of citronella candles and incense used outdoors to keep away the bugs. With West Nile virus and its risk of encephalitis, mosquitoes are more of a pest in the U.S. than ever before.

Does citronella actually work? Perhaps. First of all, there needs to be enough citronella smoke to keep the bugs at bay. That means that the more candles used, the better. The difficulty is that in open areas, especially if there's a breeze, it's tough to maintain a high enough level of citronella smoke to keep an open space free of mosquitoes. I suppose if you're right by the smoke, you'll be less likely to get attacked. But in all likelihood, that's not going to happen. Research done in Ontario found that compared with nontreated subjects, those using 3 percent citronella candles had, on average, 6.2 bites in 5 minutes versus 10.8 bites in the control group; those using 5 percent citronella incense had, on average, 8.2 bites. Those translate to a 42.3 percent and 24.2 percent reduction in bites, respectively. Still, they got more than a bite a minute. While that may be enough protection for some, I don't really want any bites.

What works best? Since mosquitoes grow and multiply in standing water, make sure there are no nearby puddles or bird water feeders to attract them. Bright-colored clothing attracts bugs, so wear neutral, light-colored clothing to avoid advertising your blood. The best insect repellents are lotions or sprays containing DEET. They're not recommended for use on infants and toddlers. Four percent DEET sprays or lotions can be used sparingly on small children. The EPA states that DEET is safe for adults when used as directed.