Is It Safe? Sun Screen

Q: My child is fair skinned and burns easily. Should I look at anything other than SPF rating when buying sun block?

A: Let me start out by saying that use of sun block and protective clothing are important to preventing skin cancer this time of the year. And yes, selection of sun block is a bit more involved than sun protection factor (SPF). The type of chemical used to block the sun is important to consider in these products. You can achieve the same SPF with a mineral-based (zinc or titanium oxide) or chemical-based blocker. However, questions have been raised about some of the chemical blockers (e.g., oxybenzone) as having weak estrogenic activity. This would not be of much concern but for the fact that large amounts are put on the skin and have the chance to be absorbed into the body, theoretically affecting hormone balance. Sun block has never been shown to cause hormonal effects but it may be best to sidestep this theoretical concern and choose the mineral-based (zinc and titanium) blockers. They are just as effective in blocking UV rays and are not associated with toxic effects when placed on the skin. Concerns have been raised that the minerals are in the form of nano-sized particles in sun block, but this does not lead to increased absorption across the skin. Another ingredient to watch out for in sun block is Vitamin A. Regarding SPF factor, it shouldn’t be a major focus as what limits efficacy is how long a sun block stays on the skin. An SPF of 15 means you can stay in the sun 15 times longer without burning as compared to no sun block (e.g., if you burn in 10 minutes without sunscreen, SPF 15 would provide 150 minutes of protection). However, sun block tends to wear off before this from swimming, sweating and various activities. What is more important than the SPF rating is that the product is water resistant and that it is applied frequently. Under these conditions an SPF rating of 15 to 30 should be ample protection.

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Dr. Gary Ginsberg is a public health toxicologist in Connecticut and a lecturer at the Yale School of Public Health. He has written a book geared toward the general public, “What’s Toxic, What's Not,” and also has a website, whatstoxic.com, to answer questions about chemicals found in consumer products and in our homes.

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The Yale School of Public Health invites you to submit questions for Dr. Ginsberg as part of this recurring monthly series. Contact us through Facebook or by e-mailing Michael Greenwood at michael.greenwood@yale.edu