Competition for higher SPF claims among sunscreen products is as intense as the summer heat. The advertising messages tend to mislead many into thinking that a 100+ SPF is twice as good as the one with a 50 SPF. But that is farthest from the truth.
Let’s look at the facts. A sunscreen with SPF 15 blocks about 93% of UVB rays; SPF 30 blocks 97% of UVB rays; and SPF 50 blocks about 98% of UVB rays. Beyond SPF 50, any additional sun protection would be insignificant. No sunscreen will block 100 percent of UVB rays.
If you have fair skin, you normally would develop sunburn in 10 minutes, in full sun without sun protection. A 30 SPF sunscreen would provide protection 30 times longer. That means 300 minutes before you start to burn. That’s 5 hours. A 50 SPF would protect you for 500 minutes. That is more than 8 hours!
The USFDA has already proposed prohibiting sunscreen claims beyond SPF 50, which tend to be “misleading to the consumer,” given that there is an “absence of data demonstrating additional clinical benefit” (FDA 2011a), and that “there is no assurance that the specific values themselves are in fact truthful…” (FDA 2007).
Do not get the idea that with a high SPF rating, one application of sunscreen would be enough to protect you all day. You of course need to reapply after swimming, drying off or sweating. You also need to reapply every two hours. Sunscreen ingredients are like sponges that absorb radiation and lose their protective power as they reach saturation point.
Note that SPF measures only protection against UVB rays, which cause sunburns, but not UVA rays, which can be more damaging to body tissues and cause wrinkles and premature aging. UVA rays penetrate deeper into the skin than UVB rays. Protection against UVA rays could be a more important consideration when choosing your sunscreen, especially for daily use.
How is protection against UVA rays measured? Most brands have adopted the PA system (Protection Grade of UVA) to measure protection against UVA rays. The PA system is based on the persistent pigment darkening (PPD) method, which uses UVA radiation to cause persistent darkening of the skin. A PPD rating of 10 should allow a person 10 times as much UVA exposure as would be without protection. PA+ corresponds to a PPD rating between 2 and 4, PA++ between 4 and 8, and the highest rating at PA+++, more than 8.
Be skin smart in choosing your sunscreen product. And remember that the first line of defense against harmful radiation would be shade, protective clothing and avoiding the midday sun.
Skin Smart seeks to clarify facts and myths on skin care. This column was published in the Manila Bulletin Lifestyle Section on April 23, 2013. The author received the 2011 Outstanding Chemist Award from Professional Regulations Commission (PRC) for his achievements in the field of cosmetic chemistry. The author is the CEO of SkinStation and can be reached at firstname.lastname@example.org.