Newswise — Everyone wants the most out of summer and sunscreen and mosquito repellent represent our best line of defense for fun in the sun. But when the two are used together, does the sunscreen work as well and should we be concerned about the chemical in the insect repellent?

Dr. Xiaochen Gu, of the Faculty of Pharmacy at the University of Manitoba (in Winnipeg, Canada), has some concerns about using both products simultaneously. He notes: "In our lab we have found that when these products are combined, there is increased absorption through the skin and that can do more harm than good." As awareness grows about proper protection against UV rays and the West Nile virus, Gu said it is important that the products we use benefit our skin and improve our quality of life. Sunscreens and repellents are designed to stay on the surface of the skin. DEET (N, N-diethyl-m-toluamide) is the active ingredient in most popular repellants, but if it is absorbed, it can cause skin allergy, hypotension, headaches, disorientation and encephalopathy, especially in children.

Gu studied DEET and oxybenzone, a sunscreen agent, separately and then combined the two, measuring their penetrative value. In his tests, the combined products showed a marked increase in absorption rates. This could mean that the side effects of the chemicals may be heightened when they are used together.

Because of this concern, Gu is now trying to modify the non-medicinal ingredients found in sunscreens and repellents in an attempt to reduce these unwanted absorption rates. This would make the products more effective and users would have to put less on to get the desired protective effect. In particular, Gu is focusing on how these products affect children and seniors.

"Children have a large body surface area and tender skin making them more prone to cross-skin absorption. People over 65 tend to have thinner skin and have had years of exposure to the sun which also makes their skin absorb more of these chemicals," he said.

Using $22,300 in funding from the Manitoba Institute of Child Health, Gu is working in the university's $485,000 state-of-the-art laboratory that was funded by the Canada Foundation for Innovation and the province in 2000.

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