We have received numerous questions about applying sunscreen together with bug spray. Here are two:
Q. I live in Florida and play golf at least four times a week. I also love to garden. Whenever I go outside, I apply sun block and then spray a potent insect repellent containing DEET. Is there any problem applying it over my sunscreen?
Q. Is there a product containing both sunscreen and bug control (DEET) on the market? Are there any problems applying sunscreen and then 25 percent deet spray? I want to be sensible and avoid both sunburn and mosquito bites.
A. Several combination products with both insect repellent and sunscreen are available. The Centers for Disease Control and Prevention (CDC) don’t recommend them because “sunscreen requires frequent applications while DEET should be used sparingly.”
Research shows another problem with such combination products (British Journal of Dermatology, June 2005). Mixing oxybenzone (a common sunscreen ingredient) with DEET dramatically increases absorption of both chemicals through the skin.
A study (J. Pharm. Pharmacol. May, 2004) suggests that the sunscreen ingredient oxybenzone enhances the absorption of DEET through the skin. Whether this represents a hazard is unknown.
In addition, DEET can reduce the effectiveness of sunscreen applied at the same time (Lancet, June 7, 1997). If you need both, apply your sunscreen first and allow it to dry before putting on the repellent. This reduces DEET absorption, though it may increase the passage of oxybenzone through the skin.
The Environmental Working Group has been analyzing sunscreens for years. Some time ago it reported that there were 600 sunscreens in the U.S. that contain oxybenzone. This ingredient has been labeled an endocrine disruptor. That means it may affect hormones. In particular, oxybenzone may mimic estrogen. It worries us that DEET could enhance absorption into the body of an endocrine disruptor.