Skip Products That Combine Sunscreen With Insect Repellent. Here's Why.

Sunscreen and insect repellent need to be applied in different quantities and frequencies, and combining them could reduce their effectiveness or change the way they are absorbed by your skin, says Esther Freeman, MD, PhD, an associate professor of dermatology at Harvard Medical School. 

The Centers for Disease Control and Prevention also advises travelers to steer clear of these products, since sunscreen generally needs to be applied more often and in larger quantities than insect repellents. Sunscreen typically needs to be applied every 2 hours, says Ross Radusky, MD, a dermatologist and medical director of the Dermatology Treatment and Research Center in Dallas; insect repellents are often designed to last 6 to 8 hours.

Reapplying a combo product every 2 hours could expose you to too much insect repellent, while reapplying every 6 hours might mean you wouldn’t be adequately protected from the sun. 

Insect repellents are safe when used as directed. But any product applied to your skin could potentially cause some sort of irritation or allergic reaction. Applying them too frequently increases the chances of these reactions, according to the CDC.

Plus, some research indicates that combining the common insect repellent ingredient DEET with sunscreen can reduce the sun protection factor by about 30 percent.