(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
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.
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
UVB rays heat up the melanin in
your skin, causing sunburn, but can also damage DNA in skin cells, contributing
to skin cancers.
is essential to look for “broad spectrum”
sunscreens that protect you from both UVA and UVB rays.
Physical or Chemical Block
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 dioxide
or 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.
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
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
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!