When I moved to Denver, Colorado almost 11 years ago, I knew that we were in the Mile High City. What took me by surprise, though, was not the altitude but rather the intensity of the sun. I had no idea that being a mile closer to the sun would make that much difference, and of course it didn’t. What makes the huge difference at higher altitudes is that there is less atmosphere to protect us from ultraviolet (UV) radiation.
UV radiation comprises light from the sun with wavelengths of 200 to 400nm, below our ability to see. While many wavelengths bounce off the surface of the body, certain portions of the light spectrum in the UV range penetrate the skin and “resonate”, magnifying the DNA damage caused by UV light. Two UV light regions are particularly important: UVB light causes sunburn, while UVA light is responsible for aging, photosensitivity, and photoallergy.
Skin damage is bad. For those with very fair skin in intense sun, sunburn from UVB radiation can occur in as little as just a few minutes. Meanwhile, UVA sun exposure also sets the skin up for various skin cancers, such as squamous cell carcinoma and basal cell carcinoma.
Prior to our era of vitamin supplementation, many children would be vitamin D deficient and develop rickets, sometimes becoming bow-legged. Since sun exposure produces vitamin D in the body, it became “healthy” to get a lot of exposure to the sun. But it was later shown that in addition to helping with Vitamin D, sun exposure also increased the incidence of skin cancers.
Sun protection starts with staying out of the sun and wearing appropriate clothing so that you do not burn. Hats are in order during sun season, and should be chosen with a wide enough brim to shield the face and ears.
Sunscreens protect us from UV radiation and can decrease the incidence of skin cancers. There are two factors to consider when choosing a sunscreen or sunblocker: its ability to block UV radiation and which wavelengths it is effective.
The ability of sunscreens to block UV radiation are rated based on SPF – Sun Protection Factor – which describes the additional time you can be in the sun before burning. An SPF of 30 means that if you typically burn in just two minutes (yes, there are people like that!) you can stay in the sun for an hour before you would develop the same degree of sunburn. It is recommended that individuals use the highest SPF available, although there is also some question as to how high an SPF is really beneficial. Most health care professionals will recommend an SPF of at least 30.
Sun protection products are also labeled for UVB and UVA protections. This can be somewhat misleading since the SPF measures only UVB protection. Since UVB radiation causes sunburn, which is something patients can see (and feel!) so most individuals can tell if they’ve been protected or not. UVA radiation is different. The damage caused by UVA exposure is more long-term and includes skin aging and cancers. It is most important to protect your skin from UVA radiation and its slow hidden damage.
There are many ingredients that are present in sunblockers or sunscreens. Chemical sunscreens use a variety of chemicals for UVB radiation and avobenzone as a UVA blocker. Chemical sunscreens can lose their effectiveness with sun exposure, so they should be re-applied at recommended intervals during the day. Physical sunscreens use zinc oxide and titanium dioxide, which block both UVA and UVB radiation. The physical sunscreens have the advantage that many patients with sensitive skin can tolerate them, but depending on the formulation they can also make patients look very white and zombie-like for a short time after they are applied. Many cosmetics include chemical or physical barriers to UV radiation.
Skin damage is one of the tell-tale signs of aging. But skin damage can be minimized through good sun habits and the use of protective clothing and sunscreens. Remember that we do not feel UVA skin damage, so it’s important to treat all sun exposure as potentially aging our skin. Take good care of yourself.
Article written by Peter J. Rice, PharmD, PhD, BCPS, FAPhA
University of Colorado School of Pharmacy