Phil Bethell sprays on mosquito repellent during a stop at the Greenwood, La., tourist center in 2002. If he were using sunscreen and repellent, it would be a good idea to apply the sunscreen first (and reapply it later).

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If you spend time outside, especially in warm weather, you may find yourself needing both insect repellent and sunscreen. We know that sunscreens are safe for everyday use, but the issue becomes thornier when mixing repellent and sunscreen.

In general, you can use insect repellent and sunscreen together. It's best to apply sunscreen before repellent. That's in part because repellent should be applied less generously than sunscreen.

Don't put repellent on your face or on babies. Instead, spray it on other parts of your body and even your clothes, though not on skin that's covered by clothing. Be careful of spraying it near cuts and on your hands, which can lead to it spreading to sensitive areas, like your eyes or nose.

The repellent should contain instructions for application, and it's important not to stray from them. You should also wash off the repellent after you're done with your outdoor activities.

Many insect repellents contain DEET, which has been controversial in the past, but it is safe to use in small doses, such as repellents containing 10 percent to 25 percent DEET [source: Illinois Department of Health]. DEET works by confusing insects' sensors, preventing them from landing and biting (although they may still be seen nearby). Children, especially small children, should avoid repellents with greater than 10 percent DEET.

In general, you shouldn't suffer any negative effects from reapplying sunscreen. In fact, it might be necessary if using it in tandem with repellent. But insect repellent should not be reapplied more than instructed, particularly if it contains DEET.

Now let's look at combination insect repellents/sunscreens.