Each summer, Americans spend hundreds of millions of dollars on lotions, potions, gizmos, zappers, clickers, clackers, candles and plants -- all to keep mosquitoes away. They may as well set a match to their cash, says Notre Dame's Clark professor of biology, George Craig.
Over the years, Craig and his Vector Biology Lab colleagues have tested the effectiveness of countless mosquito repellents. With just a few exceptions -- notably those that contain the chemical nicknamed "deet" -- they've found them all worthless.
Mosquitoes are such a nuisance, however, that people are willing to pay any price, buy any product and believe any claim just to be free of them. Take that desperation, add some ignorance, throw in a twist of gullibility, and you wind up with a product like the Mosquito Hawk, "a fiendishly cunning electronic device that mimics to perfection the sound of the dreaded little bloodsucker's greatest enemy, the dragonfly." Or so says its manufacturer.
There's only one problem with the Mosquito Hawk: it attracts mosquitoes better than it repels them. When six of Craig's graduate students tried it out at the University's environmental research station in Land o' Lakes, Wisconsin, they found that more mosquitoes landed on them when the device was turned on.
And then there's "Mosquit-A-Way," another little gizmo that uses "a unique battery-powered circuit that is superior to the pulse-modulated burst circuit in common use." Huh? Translate the maker's pseudo-scientific garble and what you get is one more another ineffective battery-powered noisemaker.
Perhaps the most imaginative claim belongs to a product called "Bye-Bye Mosquitoes." Says the manufacturer, "A spawning female mosquito is very disgusted at the approaching of a male mosquito. Therefore the frequency of Bye-Bye Mosquito is made to imitate the sound of a single male mosquito to repel female mosquitoes away."
But if that's true, where do all the little mosquitoes come from? Apparently female mosquitoes aren't as disgusted as the manufacturer claims, because they ignored the sound when the device was tested. And, as we all know, there are plenty of little mosquitoes.
While the small clip-on electronic sound repellers don't work, so-called "bug zappers" do -- sort of. These devices use ultra-violet light as a lure and are quite effective in electrocuting flies, moths and various beetles.
Unfortunately, the zappers, which cost $100 and up, aren't too good at killing mosquitoes. Ultraviolet light has no allure for them, Craig explains. Mosquitoes are attracted by a combination of heat, carbon dioxide, ammonia and other chemicals emitted by skin. Roger Nasci, a colleague of Craig's, found that mosquitoes comprise only 3 percent of the insects killed by the machine. Nasci ran zappers continuously in six adjacent yards for 11 straight days without any discernible effect on the mosquito biting rate.
Concern over the environment has lately increased the popularity of "natural" repellents, all of which are about as effective as the zappers and gizmos. Craig is distressed because the federal Environmental Protection Agency recently eliminated its natural repellent registry program. "Fraud abounds in the industry," he asserts. "At least this program curtailed the more extreme and dishonest claims. Now the public is without even this minimal protection."
Citrosa plants, for one, have been widely marketed as repellents. Ads claim that the plants, which can cost up to $35 apiece, provide mosquito protection as much as 50 yards away. Pooh-poohs Craig, "They're really nothing but smelly geraniums. There's no evidence that they repel mosquitoes." Even when the plant was ground up and the paste applied to human skin it showed no effect; the mosquitoes feasted away undeterred.
There are some products, however, that really do work. Of these, the most effective are those containing N,N diethyl-meta-toulamide, or "deet" for short. The chemical is the active ingredient in such popular brands as "Off" and "Cutter's," among others.
Best of all, a little deet goes a long way. "You really don't have to buy the more expensive, concentrated 'deep woods' variety of these repellents," advises Craig. "Studies have shown that a 15 percent concentration works just as well as 100 percent concentration. Depending on a person's individual chemistry, the sprays usually are effective for about two hours."
But even deet is not the ideal repellent. The chemical is absorbed through the skin into the bloodstream and has been linked to health problems: skin rashes, seizures, neurological damage and, in rare cases, death. Children are most susceptible to its toxic effects. When used as directed, however, deet is safe; problems arise when it is applied too liberally.
Surprisingly, another effective repellent is Avon's "Skin-So-Soft" body lotion. The product does not contain "deet," and scientists aren't exactly sure why it works, but it does have a short-lived repellent effect.
What about some of the other legendary "folk" repellents? Downy fabric softener, a favorite among Wisconsin and Minnesota fishermen, will make your clothes nice and fluffy, but that's about all. And the old standby citronella candle has a distinctive summertime aroma that mosquitoes love to ignore.
Although citronella doesn't work in candle form, when the oil is applied to the skin it does repel slightly. Scientists surmise the oil sets up a barrier on the skin.
When all else fails, of course, there's always "SWAT," the old reliable five-fingered repellent/insecticide. True, it's only marginally effective; usually you nail the sucker only after it's bitten you. On the plus side, it needs no batteries, it contains no dangerous chemicals, and it's user-friendly.
Then again, maybe the best bet is just to forget this "great outdoors" stuff, go inside, pour yourself a tall, cold drink and watch an episode of National Geographic