How high of an spf does your sunscreen need to give you good protection from UV rays? You know that wearing sunscreen daily is one of the most important anti-aging and preventative health moves you can do for your skin. It’s important to pick the best product and people ask for my advice to help them do that. One of the biggest sunscreen questions people have is about SPF numbers.
Common sense, AND what you learned about numbers in math class, would lead you to believe that sunscreens with really high numbers must give really powerful sun protection, right?
Sunscreen companies would like you to believe that too, but.......
Why doesn’t a SPF 60 sunscreen give you twice as much sun protection as a SPF 30?
Answer: The protection you get isn't proportional to the numbers.Find out what you should look for and stop being fooled by misleading product marketing claims. Pick the best sunscreen for your skin, wear it daily, know you’re protected, and your skin really will look fabulous as you age.
SPF and UV FAQs
Important facts for understanding your sunscreen needs:
- UVB is the sunburn ray. You’re most exposed when you're close to the sun because UVB rays are absorbed as they pass through the earth’s atmosphere-the closer you are to the sun the stronger the UVB. It’s why the sun is more intense near the equator, at high altitude, in summer and at mid-day.
- The SPF value indicates how well your product protects you from UVB.
Dermatologist explanation of how sunscreens work.
How do chemical sunscreens block UV rays?
- Organic sunscreens absorb into your outer dead skin cell layer and use a chemical reaction to block UV rays from passing farther into your skin. (The term 'organic' doesn’t mean natural, it means not mineral.)
- You feel this reaction as warmth, which is why organic sunscreens may make you feel a little extra hot in the sun.
- The organic chemicals break down during this sun blocking chemical reaction, which is one reason why sunscreen products tell you to reapply every 2 hours when you're out in the the sun.
- All the 'active ingredients' listed on sunscreens that are not zinc oxide and titanium dioxide are chemical sunscreen filters.
How do mineral (physical) sunscreens block UV rays?
- Mineral sunscreens sit on top of your skin and bounce the sun off, without a chemical reaction and without creating the warmth.
- Mineral sunscreens include zinc oxide and titanium dioxide. Years ago, mineral sunscreens were white on the skin. Today's modern versions are made with high-tech formulations so that the mineral particles don't clump together. Instead, they distribute evenly and invisibly over your skin surface.
- Mineral UV filters don't pass into your skin
- Zinc oxide and titanium dioxide to not readily break down when they block the sun so their sun protection last longer on your skin.
Both organic and mineral sunscreens can block UVB well and can provide the same SPF values.
The amount of UVB protection isn't proportional to the SPF number.
Is SPF 4 sunscreen really different from SPF 15 or 30?
Said another way, what is the percentage of UVB that’s blocked from your skin compared with your product's SPF value?
SPF 2 means 50% of UVB rays are blocked
SPF 4 means 75% of UVB rays are blocked
SPF 10 means 90% of UVB rays are blocked
SPF 15 means 93% of UVB rays are blocked
SPF 30 means 97% of UVB rays are blocked
SPF 50 means 98% of UVB rays are blocked
SPF 70 means 98.5% of UVB rays are blocked
SPF 100 means 99% of UVB rays are blocked
Notice that once you hit an SPF of 10 a sunscreen blocks 90% the percent of UVB rays. After that, the percent of UVB blocked doesn’t go up very much as the SPF numbers go up. The sweet spot is SPF 30 where 97% of the UVB rays are blocked, and most dermatologist’s agree.
Remember, to get the actual SPF protection from sunscreen you must apply the correct amount of sunscreen.
This is a really important point to understand. For the average adult, that means 1 oz (a shot glass) per application when in a bathing suit, and reapplied every 2 hours or after water contact. That means a day in the beach should use up ½ to ¼ of an 8 oz. bottle of sunscreen!
Plus, organic sunscreens break down as they block the UV rays. Mineral sunscreens are structurally more durable and can last longer on your skin. They are usually combined in products with organic sunscreen ingredients so we still recommend reapplication every 2 hours, but I think the added protection matters. All the dramatic sunburns that my patients have brought to my office over the years happened with the use of 'organic' sunscreens.
UVA protection is critically important for anti-aging and skin cancer prevention.
UVA skin damage:
- UVA causes the wrinkles and skin thinning that most people think come with age
- UVA plays a role in causing skin cancers
To know if a sunscreen blocks UVA look for the word 'Broad Spectrum' on the front label.
UVA is very damaging to skin. The UVA rays are out all day, all year, and the SPF on a product tells you very little about UVA protection. A sunscreen product can claim to give UVA protection even if it doesn’t protect you from all the bad UVA rays. Look for a product labeled Broad Spectrum AND SPF 30 or higher to be certain you are also getting good UVA protection. I also recommend that the product be formulated with at least 5% or more zinc oxide because:
- Zinc oxide is the only ingredient that blocks all the way through the UVA wave spectrum to 400nm, though titanium dioxide goes almost to 400nm too.
- So far the organic UVA sunscreen ingredients like avobenzone have stability trouble and may not last in the bottle and on your skin, and we don’t yet have ways to measure this.
What is my opinion on sun screens, and the ‘bottom line’ as a careful dermatologist?
An SPF 30 that includes 5% or more of zinc oxide, applied every day, will take good care of your skin.
Links to sun protection products that I, as a dermatologist, use and recommend to my dermatology patients:
Some of the favorite sun protection kits include:
SunSavvy Around Town Kit: great daily wear products including 3 sunscreens that are pure mineral products: a facial sunscreen and a moderately water resistant product and a lip SPF. I include a great sun hat and my Detecto Ring to test UV ray exposure.
SunSavvy Ultimate Sun Kit: 2 zinc oxide sunscreens (two water resistant for sweaty and wet outdoor activities and one with a more matte finish for everyday use), mineral sunscreen for your lips, Sun Guard to wash into your summer clothing to make them sun protective and The Detecto Ring to test your sun exposure.
SunSavvy Active Protection Kit: Perfect protection for wet and sweaty fun with 2 water resistant zinc oxide sunscreens, lip protection a hat and the Detecto Ring.
To see all of my dermatologist-recommended sun protection products click here. These are the products I trust for my patients, my family and my own skin.
Photo: NASA Goddard Photo and Video