How High of an SPF Does Your Sunscreen Need To Have?

Cynthia Bailey, MD|April 12, 2011

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 they 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…...

Question: Why doesn’t an SPF 60 sunscreen give you a lot more sun protection than an 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. 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.

How sunscreens work:

Organic sunscreens (this doesn’t mean natural, it means not mineral) go into your skin and use a chemical reaction to block UV rays from passing farther into your skin.  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 why sunscreen products tell you to reapply every 2 hours when you're out in the the sun. 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 have been ‘micro sized’ with nano-technology so that the mineral particles are so small that it’s hard for your eye to see them on your skin.  They don't pass into your skin and they don’t readily break down when they block the sun so their sun protection last longer on your skin. Both organic and mineral sunscreens block UVB well and can provide the same SPF values.  The amount of protection you get isn't proportional to the SPF number though. 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 then 90% the percent of UVB rays blocked.  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 though that you have to put the correct amount of sunscreen on for this protection. 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 stronger and 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. UVA protection is also critically important for anti-aging and skin cancer prevention because UVA:

  1. causes the wrinkles and skin thinning that most people think come with age
  2. plays a role in causing skin cancers

UVA is out all day, all year and the SPF on a product tells you noting 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.  Sunscreen formulation is complicated and to keep things simple I recommend that people just look for a sunscreen product that says it has 5% or more micro zinc oxide in it 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.

My opinion on sunscreens and the ‘bottom line’ as a careful dermatologist:

An SPF 30 that includes 5% or more of micro 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:

The Ultimate Sun Kit: 2 micro zinc oxide sunscreens (one 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. The Sun Protection Kit For Normal Skin: 2 micro zinc oxide sunscreens (one water resistant product for sweaty and wet outdoor activities and one with a more matte finish for everyday use). Glycolix Elite Sunscreen: Pure mineral protection with 17% micro zinc oxide for everyday use. For more information on my recommendations for smart sun protection: 5 Steps For Smart Sun Protection If You Want A Nice Sunburn, Use Last Year's Sunscreen Are Your Summer Clothes Good Enough To Be Sun Protective Clothing Great Sun Hats; what works and what doesn’t Photo: NASA Goddard Photo and Video

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