Applying sunscreen is a key part of having a safe and happy summer.

Today’s blog post is written by Dr. Donald B. Levy, Medical Director of the Osher Center for Integrative Medicine at Brigham and Women’s Hospital. Most of us will endure many bug bites and stings, and an occasional overdose of the sun, during the summer and fall. Here are a few hints from the Centers for Disease Control and Prevention (CDC) and other sources to stay healthy.

Use Sunscreens Effectively and Intelligently:
  • Throw away sunscreens older than 1–2 years since they lose their potency over time.
  • Learn about SPF (Sun Protection Factor), ultraviolet A (UVA), and ultraviolet B (UVB) protection. SPF refers to how long a person will be protected from a burn from UVB. SPF 15 means a person can stay in the sun 15 times longer before burning. SPF 30 sunscreens are not twice as protective as SPF 15. When applied properly, the amount of UVB radiation absorbed by sunscreens with SPF 15 is 93 percent; sunscreens with SPF 30 absorb 97 percent UVB rays, and sunscreens with SPF 50 absorb 98 percent of UVB rays. Products with SPF >50 provide almost no additional increase in the protection from UVB.

  • To protect against UVA, 95 percent of the total UV radiation that reaches the earth at sea level, look for products containing: Mexoryl, Parsol 1789, titanium dioxide, zinc oxide, or avobenzone. Under new regulations in effect by December 2013, only sunscreen products that pass the Food and Drug Administration’s test for protection against both UVA and UVB rays will be labeled as “broad spectrum.”
  • Reapply sunscreen at least every 2 hours and each time you or your children get out of the water or perspire heavily.
  • Current evidence suggests that most sunscreens are safe and not absorbed into the body.  Most of the ingredients known to cause allergic reactions and irritant contact dermatitis (PABA, amyl-dimethyl-PABA, or benzophenone-10) are now rarely used in sunscreens. Oxybenzone (benzophenone-3), the most widely used UVA filter, is the most frequent cause of sunscreen-induced photoallergic contact dermatitis but this rate is low (<0.1 percent).
  • For those who do not like extensive use of skin creams, there are hats, sunglasses, and protective clothing that protect the skin from sun damage. The Skin Cancer Foundation lists products that have met its seal of approval with an ultraviolet protection factor (UPF) of 30 or higher.
Keeping Insects at Bay with Insect Repellents

The CDC recommends using products that have been shown to work in scientific trials and that contain active ingredients that have been registered with the US Environmental Protection Agency (EPA) for use as insect repellents on skin or clothing. When EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment.

Of the active ingredients registered with the EPA, the CDC believes, based on published scientific literature, that products containing one of the following ingredients provide longer-lasting protection in repelling ticks and mosquitoes.

  • DEET (N, N-diethyl-m-toluamide), developed by the US Army in 1946 is considered the gold standard. There have been reports of toxicity when DEET is used in high concentrations, however, most authorities consider it safe to use in products containing less than 30 percent concentrations for adults  and 10 percent concentrations for children. DEET, however, is greasy, smelly to some, can stain fabric, and may dissolve some plastics and finishes.
  • Picaridin (KBR 3023) is a plant-based compound has been used in Australia and Europe for years and became available in the US in 2005. The CDC recommends it as an alternative to DEET. In concentrations of 15-20 percent it can be as effective as DEET in repelling ticks and disease-carrying mosquitoes. Unlike DEET, it is odorless, non-greasy, non-sticky, doesn’t degrade plastics or fabrics, and no allergic reactions have been noted. Look for products that have 15-20 percent concentrations as lower doses are less effective.
Using Insect Repellents and Sunscreens Together

People can, and should, use both a sunscreen and an insect repellent when they are outdoors. Follow the instructions on the package for proper application of each product. In general, the recommendation is to apply sunscreen first, followed by repellent.

It is recommended NOT to use a single product that combines insect repellent containing DEET and sunscreen, because the instructions for use of insect repellents and use of sunscreen are different. (In most situations, insect repellent does not need to be reapplied as frequently as sunscreen.)

Read more blog posts from the Brigham and Women’s Osher Center for Integrative Medicine:

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