Bug spray and Sunscreen DON’T mix!

Hot summer days are upon us, and with them comes the desire for day hikes, camping trips, or just lounging on the deck. These are all wonderful things except for the ever-present mosquitos. So, what to do? We want to protect our skin with sun screen, and deter the bugs with bug spray, so the obvious solution would be a combination sun screen-insect repellant, right? WRONG!

According to Pierre George, M.D., (George, n.d.) the combination of sun screen and insect repellent can be problematic. He says:

“While both sunscreens and insect repellents are effective and safe when used separately, if combined, the sunscreen’s ability to screen out ultraviolet (UV) radiation can be decreased by the repellent, while the toxicity of the repellent is increased by the sunscreen. …especially in children.”

DEET (N,N-diethyl-m-toluamide), is the main active ingredients used in many bug repellants. It is EPA-registered, and helps keep insects away when used correctly, i.e. according to the manufacturer’s instructions. Although there are other insect repellents on the market, DEET is the most common and is safe with minimal toxicity, but its potency can be amplified when combined with sunscreen.

Ross (2004) tested solutions of either 20% DEET or 10% DEET mixed with sunscreen on hairless mice. Even though the DEET in the mixed solution was only 10%, it was detectible in the skin in as little as 5 minutes, compared to 30 minutes for the 20% solution. His study also showed that once the DEET penetrated the skin it was absorbed 3.4 times faster in the10% mixed solution than the 20% solution.

These numbers sound really scary, so what to do?

First, realize that DEET is safe. “DEET has an unbelievably superb safety record; it’s been used on millions of people and it’s critical that people don’t get the wrong message. People should continue using DEET because of the very real risks of mosquito and insect-borne illnesses, such as West Nile encephalitis, but use it in the lowest effective concentration, especially when you use it in combination with other topical lotions or in children” (Ross, 2004).

Second, apply sunscreen and insect repellent separately. “Sunscreens should be applied generously and frequently: a full ounce (two tablespoons) of sunscreen should be applied directly to the entire body, including a nickel sized dollop to the face, at least every two hours. Insect repellents (DEET), on the contrary, should be applied no more frequently than every two to six hours, depending on the concentration, and you should avoid applying it to the face.” (George, n.d.).

Now go camping!

~Monica

George, M.D., Pierre. ASK THE EXPERT: Would it be better to use a product that combines insect repellent and sunscreen, or two different products? (n.d.) Skin Cancer Foundation. Retrieved from http://www.skincancer.org/skin-cancer-information/ask-the-experts/would-it-be-better-to-use-a-product-that-combines-insect-repellent-and-sunscreen-or-two-different-products.

Ross, E. Drug Metabolism and Disposition. (August 2004; vol 32: 783-785). News release, University of Florida Health Science Center. American Academy of Pediatrics.