ASK THE EXPERT: Would it be better to use a product that combines insect repellent and sunscreen, or two different products?

George Pierre, MD

By Pierre George, MD

Dr. George practices general dermatology and Mohs surgery at Dermatology Consultants in St. Paul, MN.  He is the author of numerous articles and is a fellow of the American Academy of Dermatology, the American Society for Mohs Surgery, and the  American Society for Dermatologic Surgery.

Q. I’ll be outdoors a lot this summer, and I want to protect myself from insects as well as the sun. Would it be better to use a product that combines insect repellent and sunscreen, or two different products? What would be the best way to apply and reapply these products?

A. Although a combination sunscreen/insect repellent sounds appealing, it is better to use two different products rather than a single combination formulation. A single product may sound like a great idea. It’s convenient, since the product protects from both sun damage and insect bites. Anyone with small children knows how unpleasant it is to get kids ready for the outdoors. A combination product would simplify that task.

However, in practice, combination products are problematic. 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. Some sunscreen preparations lose efficacy when used with DEET (N,Ndiethyl-meta-toluamide, the most effective and most common bug repellent).  In some studies, the combination has led to a reduction of more than 30 percent in SPF. (SPF, or sun protection factor, measures a sunscreen’s ability to screen out ultraviolet B, or UVB, rays.) What’s more, sunscreens enhance absorption of DEET into the skin, potentially increasing toxicity, especially in children.

The problem is compounded by the application directions. 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. It is difficult to reconcile the opposing requirements of combination formulations.

In summary, I advise you to use two separate products. First, liberally apply to all exposed areas a broad spectrum sunscreen that protects against both UVA and UVB radiation with an SPF of 15-30 or higher, and reapply every two hours. Then an insect repellent (I like a DEET spray) should be applied and reapplied following the manufacturer’s instructions.

Published in the Summer 2010 Edition of Sun & Skin News