When you're having a fun day out in the swamp, you want to keep both the sun and the skeeters at bay—and conveniently, some products combine sunscreen and the potent bug repellent DEET. However, toxicology research from the University of Florida suggests that you're better off carrying two bottles.

What the researchers wanted to know: Does mixing DEET with sunscreen let it permeate your skin more easily?

What they did: The researchers used a little set-up that let them measure chemicals moving through a fingernail-size piece of mouse skin. They pumped test chemicals in one side of the skin. On the other side was a well of diluted ethanol, which fed into machines that identified the compounds that made it through.

What they found: DEET by itself made it through the skin quite well. But it did even better in a sunscreen. While it took 30 minutes to detect DEET on the far side of the mouse skin when it was by itself, the DEET in OFF! Skintastic With Sunscreen made it through at measurable levels in five minutes. Speed isn't the only thing that matters; more DEET also made it across the skin if it had help from sunscreen than if it was applied by itself.

What the study means to you: Now, don't freak out. DEET is thought to be quite safe; even animals that are fed high doses by mouth do fine, the authors say, and it's probably better for you than West Nile virus. They do say that you should use DEET at the lowest concentration you can, which means avoiding sunscreens containing DEET, since you have to keep reapplying sunscreen to protect you from the sun. The authors make a scientific point: Toxicology studies that take one chemical at a time aren't realistic, because chemicals interact in the real world.

Caveats: This wasn't a study on actual people—it used mouse skin—and it tested only one sunscreen that contains deet. Also, it doesn't say anything about what happens to you if you get more DEET into your body.

Find out more: The American Academy of Pediatrics recommends not using DEET on kids in concentrations over 30 percent and not using DEET-sunscreen combinations.

Read the article: Ross, E.A., Savage, K.A., Utley, L.J., and I.R. Tebbett. "Insect Repellant Interactions: Sunscreens Enhance DEET (N,N-diethyl-M-toluamide) Absorption." Drug Metabolism and Disposition. August 2004, Vol. 32, No. 8, pp. 783–785.

Abstract online: http://dmd.aspetjournals.org