Ask the Doctors

Dear Doctor: Is it safe to use an insect repellent with DEET on my 5-month-old? Here in Tennessee, we're approaching prime mosquito season, and we want our little boy to be able to play outside without getting all bitten up.

Dear Reader: There's nothing like the thin, high whine of a mosquito to let you know your picnic or hike or nap on the porch is about to be ruined by slapping, itching and scratching. Unfortunately, mosquitoes are also known carriers of serious diseases. West Nile virus and St. Louis encephalitis have been diagnosed in some areas of the United States. The Zika virus, while rare in the United States, is also a mosquito-borne disease.

According to the Centers for Disease Control and Prevention, insect repellents that contain DEET are safe to use on children 2 months old and older. DEET, which is shorthand for (deep breath) N,N-diethyl-meta-toluamide, is the active ingredient in a wide array of insect repellents.

DEET does not kill insects. It works by blocking the sensory mechanisms that tell insects that something delicious is nearby. Instead of detecting the chemical markers we humans emit in our breath and sweat, the bugs smell ... nothing. They pass us by.

There are specific guidelines you should follow when using DEET on a child. The CDC recommends that you never use a product with a concentration of more than 30 percent DEET. The percentage of DEET in a product doesn't make the insect repellent stronger or more potent; what that number measures is the length of time the insect repellent will be effective.

Products with concentrations of 10 percent keep bugs at bay for about two hours. Those with 21 to 25 percent DEET provide between five to eight hours of protection. And, please note -- current recommendations state that children should not have more than one application of DEET per day.

Although some insect repellents with DEET have sunscreen mixed in, it's best to steer clear of those. Sunscreen must be reapplied throughout the day to be effective. However, since kids should only get one application of DEET per day, the mixed product is of limited use. It's best to start with a base layer of sunscreen and then add insect repellent. You can then add more sunscreen throughout the day as needed.

Insect repellent should be applied to exposed skin and to clothing. When using a spray, apply it outdoors and be sure to keep it away from food. Make sure neither you not your child inhales the product.

We find that while a spray works well on clothes, insect repellent wipes are great for precise applications to a child's wriggling body. And never put insect repellent on a child's hands, which so often find their way into mouths and eyes. Once back indoors, wash the treated skin with soap and water. Treated clothes should be washed before wearing again.

One final thought: While repellents are a great tool, give them a boost by keeping kids in long-sleeved pants and shirts when in the buggy great outdoors.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

More like Ask the Doctors