University of Manitoba pharmaceutical researcher Dr. Xiaochen Gu says using sunscreen and mosquito repellant together increases their absorption rates. That could increase the risk of side effects like skin allergy, hypertension, headaches and seizures, especially in children.

Gu studied DEET, the active ingredient in many bug repellants, and oxybenzone, an agent in sunscreen. He studied them separately and then combined the two and measured their penetrative value.

When DEET and oxybenzone are combined, there's a marked increase in the rate of absorption through the skin. Gu says this could mean the side effects of the chemicals may be heightened when they're used together.

He's trying to modify the non-medicinal ingredients found in bug repellants and sunscreens to reduce these high absorption rates. That may make the products more effective and users would have to use less of them to achieve the desired protective effect.

Gu is especially interested in how sunscreens and bug repellants 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 sun, which also makes their skin absorb more of these chemicals," Gu says in a news release.

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