Which Mosquito Repellants Work Best?

On one side of the annual battle is everybody's least-favorite summer visitor: the mosquito. On the other is Dr. Jonathan Day, one of the nation's foremost medical entomologists.

Day has spent years at the University of Florida's Vero Beach Research Center studying how to keep the mosquitoes off your neck.

"People want to be out on their deck enjoying the evening — enjoying the outdoors — and mosquitoes make it virtually impossible for that to happen," Day said.

So how well do the lotions and electronics designed to do battle with mosquitoes really work? As part of Good Morning America's partnership with Good Housekeeping magazine, we teamed up with Good Housekeeping Institute and Day, one of the nation's top bug doctors, to put the lotions and gadgets designed to fight mosquitoes to the test.

The Mosquito Bite Trials

We set up what is called a mosquito cage test. Each "trial" uses 80 hungry females, since the female mosquitoes are the only ones that bite. Brave volunteers who work with Day stick their arms into the cages, with their bare skin protected only by repellents.

Mosquitoes are ferocious insects. In one minute almost every mosquito in this cage will bite an untreated arm.

Mosquito Contro Plus: The first product tested is the "Mosquito Contro Plus" by Lentek. The $20 device looks like a watch, and emits a tiny "buzzz" sound.

The company says the sound irritates mosquitoes, and keeps them away. One volunteer, Anne, tried it first, and the mosquitoes went right for her arm.

"The mosquitoes landed around the watch, one just landed right on the watch," Day said. When another volunteer, Greg, tried it, he fared even worse, and was left with mosquito bites covering his arm.

"This isn't slowing them down — isn't stopping them," Day said. "We don't have to do much more."

Day's bottom line on the Contro-Plus?

"They are a waste of the consumers' money," Day said.

Lentek, the company that markets the product, disagreed with Dr. Day. Company officials told ABCNEWs that the product works well, and that these cage tests are unscientific. They also claim that very few consumers ever return their product.

Off! Botanicals Lotion: Next, we tried out the Off! Botancials lotion. This type of repellent uses a derivative of eucalyptus oil to shoo away the bugs. Our volunteers had good results, half an hour after applying the lotion.

But how long would it last? Both our volunteers still had good protection at the 1 hour and 45 minute mark.

After 2½ hours, Hilda is still getting some protection, but Nazar isn't so lucky. He was bitten 11 times. But Day says the Off! Botanicals did a great job by lasting as long as it did.

"The eucalypus really looks good," Day said.

Off! Deep Woods and the Cutter Skinsations: Like many products on the market, these two contain the chemical repellent N, N-diethyl-meta-toluamide, better known as "DEET". For 50 years, DEET has been considered the gold standard of repellents. Sure enough, both products offered great protection for our volunteers.

Walter, who was using the Cutter Skinsations, does get one bite on his finger, but the difference is visible when he puts his other unprotected arm in with the very same batch of mosquitoes. They basically fed on his arm.

Cutter Skinsations, which contains 7 percent DEET, gave our volunteers about one hour of protection. The Off! Deep Woods, which contains 30 percent DEET, lasted more than two hours, and according to Day, can last up to six.

Parents should know, however, that while most experts say DEET products are safe, the American Academy of Pediatrics recommends children only use products with less than 10 percent DEET.

After the tests were over, Day stressed that in some situations, the best repellent is common sense.

"My advice is always, if the mosquitoes are unbearable on your deck in the evening-go inside. Go inside and watch TV!" Day said.