Although we take sunscreen quite seriously here in Phoenix, most of what people know about sunscreen is just plain wrong.
We are better at preventing sunburns than skin cancer. Surprised? There is no strong scientific evidence that sunscreens prevent skin cancer. And most of the medical community is unaware of this fact.
The skin cancer rate is steadily climbing despite plenty of sunblock choices. Sunlight striking skin treated with sunblock still does DNA damage, as well as generates free radicals. Some sunblocks can reduce DNA damage by up to 50% and have ingredients intended to naturalize free radicals. You may pretend your sunblock is shade in a bottle, but your skin isn’t fooled.
The FDA is trying to ban any sunblock from claiming a higher SPF rating than 50. Most of us do not regard SPF grade inflation as any great threat. Higher SPF-rated sunscreens don’t outperform lower rated ones.
An SPF of 30 gives you 95% protection, 50 provides 98%, and SPF 100 is 99% effective. Sunscreens can only provide protection for two hours. After two hours, the chemicals rapidly break down or become sweated or toweled away.
So, at two hours, a person using SPF 50 has 1% more UV exposure than a person using SPF 100. If the 50 is reapplied at two hours, they will still have 98% protection.
What if the person using SPF 100 decided not to reapply after two hours? They would get a bad sunburn and be hating life.
Reapplying any sunblock beats trying to get an extra hour out of the SPF 100 ultra-sunscreen. High SPF sunscreens do not protect any longer than lower ones. People who buy “stronger” sunscreen generally apply it much less heavily, and do not reapply it as frequently as lower SPF users. That is why the government wants to end the SPF arms race.
And what about all of the chemicals in sunscreen? You do get low but measurable levels in the blood from some of them after applying to your whole body. These are not carcinogenic chemicals and are considered much less dangerous than the UV radiation they prevent. However, in the body they can act as a hormone mimic and cause mild changes in some hormone levels.
If such things are concerning, there are sunscreen products that use zinc oxide and titanium dioxide to block sunshine. These are non-absorbable and biologically inert –they don’t get into the blood stream.
If avoiding skin cancer is not motivation enough, the Australians did a rigorous study on daily sunblock use and aging. They found that daily sunblock use will make a person look five years younger on average.
So, take care of that skin. It needs to last a lifetime.
Donald Bucklin, MD (Dr. B) is a Regional Medical Director for U.S. HealthWorks and has been practicing clinical occupational medicine for more than 25 years. Dr. B. works in our Scottsdale, Arizona clinic.
Photos courtesy of the artists of Unsplash.