Askanesthetician's Blog

An esthetician explores skincare issues and concerns

Spf 100 Is A Joke August 10, 2010

Have you noticed lately that you can easily find sunscreens with a SPF of 50, 70, or even 100?  Have you wondered if those sunscreens protect you better than ones that have a SPF of 30? 

Actually you should think twice before using a sunscreen with an SPF higher than 30. 


First of All – What Does the SPF Rating Mean?


In order to understand why you really don’t need a SPF over 30 you first need to understand the SPF ratings.  The Skin Cancer Foundation does a good job at explaining what SPF means:

The SPF rating is a reliable measurement of protection against UVB (short-spectrum) wavelengths (290-320 nanometers; 1 nm is a billionth of a meter). SPF is the comparative ratio between the minimal erythemal dose (MED) in skin protected with sunscreen and the MED in unprotected skin. For example, if it takes 20 minutes without protection to produce erythema, an SPF 15 sunscreen might prevent reddening 15 times longer—about five hours. That figure is theoretical, however, and sun damage can occur even without reddening, so dermatologists normally advise reapplying after approximately two hours.The Skin Cancer Foundation considers SPFs of 15 or higher acceptable UVB protection. Such sunscreens also provide some protection against UVA wavelengths (320-400 nm), though the SPF rating refers only to UVB protection. No FDA-approved measurement standard exists yet for UVA protection in the US, even though UVA penetrates more deeply into the skin than UVB, reaching the dermis. In the past, experts believed that UVB causes burning and skin cancer, while UVA causes photoaging, but the truth has proven more complex. In addition to producing sunburn, UVB can contribute to photoaging, and both UVA and UVB exposure can lead to skin cancer.

Broad-spectrum sunscreens combine UVB and UVA-absorbing chemicals and/or physical blockers, and give the most protection. However, they do not provide complete coverage in the UVA1 range (340 – 400 nm).


How Much Sun Is Blocked?


SPF 30 does not give you twice the sun protection of SPF 15.  Dr. Ellen Marmur explains the SPF rating confusion in her book Simple Skin Beauty thusly (page 88):

SPF math is also deceptive because the numbers don’t add up.  SPF 30 does not double the protection of SPF 15, for example.  It would figure that you should be able to stay in the sun thirty times longer, but that’s not the case.  An SPF 15 allegedly blocks 93 to 95 percent of UVB rays, while an SPF 30 supplies 97 percent coverage.  So bumping your SPF to over 50 doesn’t make it that much more protective.

Furthermore, The Skin Cancer Foundation answers the following question on their website:

Q. Many people mistakenly believe that an SPF 30 rating gives twice as much sun protection as an SPF 15 and an SPF 50 more than three times that much. What is really the difference?

A. In vitro tests have shown that SPF 15 sunscreens filter out 93% of UVB rays, while SPF 30 protects against 97% and SPF 50 98%.



What’s Wrong with SPF 100


As you now understand from what you’ve read above that anything over SPF 30 doesn’t give you much more sun protection than the sunscreen with SPF 30.  So do so many people persist on using products with a high SPF and why do so many companies manufacture them?  The answer comes down to people thinking that they are getting superior sun protection and the fact that companies are more than happy to sell that false hope.   According to the Environmental Working Group:

In 2007, the FDA published draft regulations that would prohibit companies from labeling sunscreens with an SPF (sun protection factor) higher than “SPF 50+.” The agency wrote that higher values would be “inherently misleading,” given that “there is no assurance that the specific values themselves are in fact truthful…” (FDA 2007).

Since then FDA has been flooded with data from sunscreen makers seeking to win agency approval for high-SPF products, and store shelves have been increasingly packed with high-SPF products the agency has yet to validate. Johnson & Johnson (makers of Neutrogena and Aveeno sunscreens) submitted data in August 2008 to support SPF 70 and SPF 85 claims (J&J 2008). Playtex (Banana Boat sunscreen) sent data supporting high SPF claims in 2007. A Coppertone spokeswoman said, “Many manufacturers, including Coppertone, have submitted new data [on high-SPF products] for review and are awaiting FDA’s response” (Boyles 2009).

High-SPF sunscreens are popular. Sales have been on the rise for at least a decade, so it’s no wonder that sunscreen makers are fighting to keep them legal. In a letter to FDA 10 years ago, Neutrogena cited consumers’ clear demand for high SPF products, calling them “one of the fastest growing segments” of the market (Neutrogena 2000). Between 2004 and 2008, sales of high-SPF products in Europe (SPF 40 and 50+) swelled from 15 percent to 20 percent of the market (Jones 2010). In 2010, sunscreen makers have once again increased their high-SPF offerings in the US. Nearly one in six products now lists SPF values higher than “SPF 50+”, compared to only one in eight the year before, according to EWG’s analysis of nearly 500 beach and sport sunscreens.


My anger with SPF 100 (or 50 or 70) really comes down to giving people a false sense of protection.  No matter what SPF rating your sunscreen has it gets used up over time and needs to reapplied.  People also use less of sunscreens with a SPF higher than 30 which means they actually get less sun protection and are really exposing themselves to more sun damage.  Once again I’ll quote from Dr. Marmur’s book (page 128):

 A 1999 study published in the Journal of the National Cancer Institute showed that using higher-SPF sunscreens lead to increased sun exposure.  In the experiment, one group was given a low-SPF sunscreen, while the other sued SPF 30.  The group given the higher SPF spent 20 percent more time in the sun than the other group.  Even though it’s wrong-headed, we’re often guilty of spending more time in the sun than we should and not reapplying a sunscreen just because the SPF is 50 or 70.  Those are deceptive numbers for sure, and inaccurate – especially if you remember that a higher SPF give you only a fraction more protection.  In fact, for these reasons, the FDA is considering limiting SPF values to 30, with higher SPF labeled “30 plus”.


 The Bottom Line


When it comes to sunscreen use SPF 30 will give you more than adequate protection.  What is most important when it comes to sunscreen use is applying enough sunscreen (an adult needs a shot glass size amount of sunscreen for their whole body) and to reapply sunscreen throughout the day – every two hours if you are spending the day outdoors.  It is also important to look for a sunscreen that gives you protection from both UVA and UVB rays.


Sources and Further Reading


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