(For those of you who do not want to read this whole blog, there is a summary at the end of this post !) *
As I’ve previously discussed in this forum, protecting yourself from the sun’s harmful UV rays is one of the most effective means of maintaining your appearance and your health. According to the Skin Cancer Foundation, almost 20% of Americans will develop will develop a form of skin cancer at some point, making it the most common category of cancer in the US. Although the public is far more aware of the importance of sunscreen than in the past, sunscreen is still underutilized and little understood by the average consumer.
In addition, a lifetime of overexposure can lead to wrinkles, discoloration and textural chances frequently referred to as “leather skin.” In fact, recent study from Australia documenting the benefit of regular sunscreen use in slowing the aging process has been extensively covered in the mainstream media this past month and is also worth reading.
Ultraviolet or UV radiation refers to range of energy just bordering the visible spectrum. Within this spectrum there are subcategories corresponding to wavelength and energy, and consequently to their effects on human skin. Among these subcategories are UVA and UVB.
- UVA rays are lower energy than UVB, and are not associated with sunburn or erythema; however, they damage collagen leading to wrinkling and loosening of the skin, and may cause indirect DNA damage. This damage along with other mechanisms may also lead to skin cancers.
- UVB rays heat up the melanin in your skin, causing sunburn, but can also damage DNA in skin cells, contributing to skin cancers.
It is essential to look for “broad spectrum” sunscreens that protect you from both UVA and UVB rays.
Physical or Chemical Block
There are essentially two mechanisms whereby sunscreens protect the skin from the spectrum of UV rays: chemical and physical.
- Chemical blocks work by absorbing UV radiation. Studies show that they are far more effective at blocking UVB radiation, and they degrade with exposure to light and so must be more frequently reapplied. Some chemical blockers also absorb UVA rays, but there is no means of uniformly measuring this capability, as SPF measures efficacy only against UVB rays. It is important to note that SPF (Sun Protection Factor) does not denote a linear increase in efficiency. Whereas SPF 15 sunscreen absorbs approximately 93% of UVB rays, an SPF of 30 yields a 97% absorption rate. Nonetheless, I recommend using a broad spectrum sunscreen of SPF 30 or higher.
- Physical blocks are generally inorganic compounds—titanium dioxideor zinc oxide—that reflect and scatter sunlight before it reaches the skin. Physical blocks are generally less irritating to sensitive skin, and are more effective in blocking the spectrum of UV rays. Although traditionally less cosmetically appealing because they remained visible (usually bright white), new technology including micronized particles allows for less visible physical block sunscreens.
Products employing chemical blocking mechanisms are sometimes referred to as sunscreen, whereas physical blocks are referred to as sunblock; however, the most recent FDA guidelines do not permit manufacturers to label any product “sunblock” because it “overstates its effectiveness.”
Usage and Reapplication
Any sunscreen is only effective inasmuch as you use it. As per FDA guidelines, sunscreens that claim to be water-resistant must indicate if they are effective for 40 or 80 minutes, but no currently available sunscreen should be considered effective beyond 80 minutes while swimming or sweating. Furthermore, UV rays pass through most light clothing, and are not limited to the beach or golf course. Sunscreen should be worn daily, year round—especially on exposed skin like the ears, neck and face.When exercising or going in the water for any reason, sunscreen should ideally be reapplied every hour to ninety minutes.
*What to Look For on the Bottle
In summary, you’re best off using a broad spectrum sunscreen with a 30+ SPF that contains a physical block. Many sunscreens contain both physical and chemical blocks, but physical blocks are the most effective at protecting you from carcinogenic UVB and the UVA rays that cause aging. Look for zinc oxide or titanium dioxide in the ingredients. If you are prone to breakout, look for sunscreen labeled noncomedogenic (non-acne causing). Buy water-resistant sunscreen effective up to 80 minutes, and reapply, reapply, reapply!