Which Mosquito Repellants Work Best?

June 25 -- 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.