UVA/UVB - The sun has two damaging bands of ultra-violet rays. UVA penetrates the skin more deeply, causing damage in the form of wrinkles and skin cancer, while UVB rays affect the skin superficially (but are still plenty damaging) and will give you a sunburn. Most sunscreens now protect against both and, as of 2011, if your bottle is labled "broad spectrum," it must contain ingredients to provide both UVA and UVB protection.
Sun protection factor (SPF) - Be careful here: SPF seems straightforward but, unfortunately, this rating system is flawed. Using numbers like 15, 30 and 45 implies that SPF is a linear system when, in fact, this rating measures the amount of time your skin can be exposed to the sun before you begin to burn (rather than the strength of the protection). As the numbers climb higher, the protection levels off until the difference is marginal — anything higher than SPF 50 is more hours of coverage than there are hours in the day.
Also, to get full protection, you must reapply — a good rule of thumb is every two hours or after swimming. Using a higher SPF doesn't negate the need to reapply, since chemical sunscreens can degrade with UV exposure, and physical sunscreens (which block by sitting on the surface of the skin) can easily be washed away or rubbed off.
Chemical vs. physical (or mineral) - This is a point of much debate in recent years. Chemical sunscreens sink into your skin and absorb the UV rays, while physical sunscreens create a protective barrier to prevent the rays from reaching your skin.
• Physical sunscreens use zinc oxide or titanium dioxide particles suspended in a cream or gel. This makes them thicker and harder to apply. On the plus side, they last much longer (provided they're not washed away), and they're better for sensitive skin because they don't sink in and cause irritation.
• Chemical sunscreens tend to be smoother and much nicer to wear. But they contain ingredients like avobenzone, oxybenzone and mexorl that, although approved for use, many people want to avoid for health reasons (some are suspected hormone disruptors). Chemical sunscreens can also cause free radicals when exposed to UV rays, so the best sunscreens combat this by including antioxidants in the formula.
Vitamin D is another hotbutton sun issue. Our bodies make vitamin D when exposed to UVB rays, leading to theories that blocking all sun will cause deficiencies. There are plenty of good vitamin D supplements, but if you want to make it the old fashioned way, doctors say it only takes 10-15 minutes of sun per day to get what we need. After that, lather up!
In the end, the best sunscreen choice is one you'll actually use. It should look and feel good, not irritate your skin, and be cost effective so you don't skimp on coverage to save money. If you're worried about chemicals, the EWG has an updated sunscreen report for 2012 with some great non-toxic options. My personal favorites come from Paula's Choice, and her website Beautypedia also fairly rates most brands so you can compare.
The smartest way to avoid sun damage is a multi-pronged approach of sunscreen, protective clothing and smart choices — as great as it feels, it's never smart to bake in the sun, even with protection. Stay happy and sun safe all summer.
Have any swear-by-them sunscreens? Please share your recommendations in the comments...