New Weapon In The War On Biting Insects

Makers of a new insect repellent formula say they have found a way to take advantage of DEET’s proven protection against mosquitoes while harnessing many of the chemical’s ill effects to humans.

Sawyer Controlled Release DEET Formula repels mosquitoes with a non-alcohol lotion that doesn’t absorb so readily into the skin, said company spokesman Kurt Avery.

“Other formulas are absorbed because the alcohol opens the skin and lets it go through and into circulation,” he said.

“Our formula doesn’t go through. The DEET is trapped in a large ball of protein. The skin’s not going to absorb the whole protein.”

The new product releases the DEET gradually rather than simply smearing on a bath of the chemical, Avery said.

Two other products marketed in recent years have used different technologies to achieve the time-release effect:

Skidaddle encapsules the DEET in fat cells that break down gradually to release the repellent after being applied to the skin, Avery said. The technique extends the usefulness of the DEET about 25 percent, he added.

Ultrathon, no longer produced, used a formula that coated the DEET in a polymer that extended the DEET about 50 percent, Avery said. However, it was unpleasantly greasy, he said.

Sawyer’s Controlled Release is a protein-based formula that provides more than 20 hours of protection while virtually preventing the DEET from being absorbed into the skin, he said.

“The proteins are like Swiss cheese balls, with lots of little chambers inside to hold the DEET,” he said.

The protein is similar to the protein used in shampoos and is healthy for skin.

“As the skin breaks down the protection, the DEET is released all day long,” he said. “We’re in the 20- to 40-hour range.”

The Environmental Protection Agency has approved 230 registered repellents and 229 of them work under one theory of evaporation, Avery said. “Our product works on a totally different paradigm.”

Percentages of DEET in a formula are not the key to effectiveness, he said.

“What’s important is weight, the number of molecules in a space. I can take 100 percent DEET and put it on thin, or put a 10 percent formula on thick and come up with the same amount of DEET per per square inch.’

The protocol for DEET-based repellent formulas is about 1 gram for every 465 square centimeters, he said. That’s a fairly liberal application, roughly equivalent to the amount of sunscreen most people apply.

In the first 15 minutes after application, a large percentage of typical repellents evaporates or is absorbed. At least 20 percent goes into the skin, according to EPA data.

When first applied, virtually all DEET-based repellents are effective, but the effectiveness can drop rapidly as the amount of available DEET is lost to evaporation or absorption.

With most repellents, the key is to reapply, Avery said. With the new Sawyer formula, he said reapplying isn’t always necessary.

“Depending on the amount applied, a consumer can use our product and dial a threshold that will last at that level all day,” he said.

Considerably thicker applications of DEET are needed to ward off black flies he said. “We have a special repellent that’s better than DEET for flies, but it’s not in a controlled release formula yet,” he said.