Summertime. The kids are off, the pool is warm and the sun is working overtime, at least if you live in Phoenix, Arizona. I daresay we may very well be the sunshine capital of the country. Our newspapers don’t list minutes of peak sun exposure to sunburn – we list seconds. Perhaps a bit of an exaggeration, but we know sunshine in the desert.
The sun is a great big natural nuclear reactor up in the sky. Interestingly enough, the earth quakes (sun quakes) and tidal forces on the sun are literally off the Richter Scale, but the sun seems to tolerate them and should for a couple more billion years. The sun puts out radiation that they don’t make sunblock for, but by the time that radiation reaches earth, it has been reduced in intensity about 10 zillion percent. What is left is a mixture of X-rays, ultraviolet, visible light and infrared (heat) radiation. Most of the X-ray radiation is dispersed in the atmosphere. We are big fans of the visible and infrared radiation (think of a lizard sitting in a sunbeam). The ultraviolet we deal with less elegantly than the infrared.
Ultraviolet light is broken up into 3 kinds – A, B and C. They do this to confuse people and make it seen complicated. UVA is the closest to visible light; it passes most easily through the atmosphere and won’t give you a sunburn. UVA is used in tanning beds and photo therapy. Photo therapy is when you go to Hawaii because you’re depressed (and try to deduct it as a medical expense).
UVB is shorter and higher energy. The ozone layer absorbs much of it, but we get enough at the surface to still get a pretty good sunburn. UVC is entirely absorbed by the atmosphere, and a good thing too, because it is germicidal and could wreak havoc with the microbes and ecology of the world – not to mention, you could watch your skin age.
The problem with ultraviolet radiation is it damages the skin. Excessive exposure over a short time results in the well known sunburn. This is a first-degree burn to sun-exposed skin. Anyone who has ever had one can appreciate just how much skin you have. It’s the largest organ on the body, and it is well supplied with nerves, particularly pain fibers. Hydration and ibuprofen are the way to go with the usual sunburn. A really severe sunburn needs hospitalization with IV hydration and serious pain meds.
But skin is damaged by sun exposure, even if there is no visible sunburn. Ultraviolet radiation penetrates surprisingly deep into tissue, damaging cellular DNA and elastin. DNA damage is usually repaired successfully by healthy cells. Rarely, the cell is repaired incorrectly but goes on and multiplies. We call that cancer.
UV radiation also breaks down the elastin in the skin. The elastin gives the skin its tone and support. Damage to the elastin leads to premature wrinkling and aging of the skin – a fate worse than death, according to some.
Sunblock is a recent development in society and has become an essential accessory on the equipment list for outdoor activity. There is little doubt it is generally effective at lowering UVB dosages, which reduces the more common kind of skin cancer and skin aging. Beyond that, sunblock is widely misunderstood. When was the last time you read the instructions on a sunblock bottle? Although it is counterintuitive, it doesn’t block the instant you smear it on. We think of them as paint. Smear them on and instant shade. They actually bind with elements in the skin to become effective. This takes time. In general, sunblock needs to be applied 15 or 20 minutes before sun exposure for peak effectiveness.
Then there is that whole Sun Protection Factor (SPF) number. There is a complicated formula to calculate the protective value of a sunblock. I have been known to stand in front of the sunblock display and carefully consider my outdoor activity and which to buy among 15 different brands, claims of waterproof/sweat proof/anti-aging and SPFs from 15 to 60. A frustrating experience and a waste of time. Buy your favorite smell, nicest bottle or least expensive as long as the SPF is 15 or greater.
The SPF factor is almost irrelevant. The SPF value of your sunblock is the least important ingredient in whether you get a sunburn. The dirty truth: sunblock only protects you for about 2 hours. Sunblock loses effectiveness with time, water, sweat, dirt and sun exposure. If you apply SPF 15, you will block about 90% of UV radiation for 2 hours. If you apply SPF 50, you will block 95% of UV radiation for 2 hours. After 2 hours, you are on your own. High SPF numbers wash, sweat and bake off just as fast as low SPF numbers. You really can’t get longer protection from higher SPF numbers.
The next common sunblock operator error is not using enough. Too thin of a layer will not protect you fully. That means you need to use an ounce. What is an ounce? Fill up a shot glass. That’s a lot of sunblock!
Sunblock also has an expiration date on it. Don’t count on full 2-hour protection if the bottle is expired.
Keep in mind, that the best sunblock is not portable shade. It is hard to beat shade. There is a reason the outdoor workers in Phoenix wear long pants, long-sleeve shirts and hats, even in the summer. Clothing does not lose its SPF factor for years. You can even be one of those funny people who carry umbrellas on sunny days when shopping.
Summertime is a great excuse to be outdoors doing active, fun things. A little preparation will allow you to avoid a sunburn and play another day.
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.
Image courtesy of David Castillo Dominici /