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Can Sunscreen Be Combined With Deet?

Posting Date: 07/04/2005

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.?

Recent 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.

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.

Q. I read in a magazine that the phosphoric acid in colas has an adverse effect on the absorption of calcium and vitamin D, increasing the chance of getting osteoporosis. Is this a major concern?

A. Studies have suggested that people who drink a lot of soda pop, especially cola, may be at higher risk of breaking bones later in life. Scientists wondered if this were due to the loss of calcium caused by caffeine or phosphoric acid in the soft drinks.

To find out, researchers compared calcium lost in the urine after women drank water, milk, or one of four different carbonated beverages, with and without caffeine, with and without phosphoric acid (American Journal of Clinical Nutrition, September 2001). They found that caffeine increased calcium loss, but phosphoric acid had no effect.