Your
Health
Presented by University
Health Services Manoa
Are Sunscreens Safe and Effective?
There are approximately 1.8 million cases of skin cancer diagnosed each year
in the United States. Malignant melanoma, the most serious form, accounts for
about 50,000 of these cancers; it is the most common cancer among people 25 to
29 years old. Exposure to sunlight is the major preventable factor contributing
to these conditions.
Slather on some sunscreen and you're protected, right? Not necessarily. For a
number of reasons you should adopt the advice "slip, slop, slap"—slip
on a shirt, slop on sunscreen and slap on a hat. Also, avoid midday sun and long
periods in the sun. Sunscreens help, but you shouldn't count on a sunscreen for
full protection, and you should use sunscreen like any drug—read the label
and follow the directions.
One problem involves different kinds of light waves. The ultraviolet light that
causes sunburn (UVB) is not the same as the longer wavelengths (UVA) that reduce
immune system functioning in the skin and increase the risk of skin cancer. Therefore
it is important to use sunscreen that blocks both UVA and UVB light (often labeled "broad
spectrum").
However, it is difficult for consumers to know which products
labeled as UVA or "broad spectrum" blockers are really
doing the job. The Food and Drug Administration has been working
on recommendations for creating, testing
and labeling products with both UVB and UVA protection, but the guidelines
may not become effective until at least 2005. In addition, even
if all sunscreens
contained adequate amounts of UVA and UVB blockers, there are many unknowns
about how other parts of the sunlight spectrum affect the skin.
Imperfect as they are, sunscreens offer a good deal of protection
if they are applied liberally and often. However, one study indicates
that people usually
apply about half as much sunscreen as they should to get the level of protection
indicated on the label. Users also tend to apply sunscreens just as they
head into the sun; however, many sunscreens (and lip protection)
should be applied
30 minutes before going in the sun, and some at least an hour beforehand.
Further, the labels "waterproof" and "all-day protection" should
not be taken literally; these products should be reapplied after
1-2 hours, and after
sweating, swimming or toweling off.
Even if sunscreen is applied adequately and frequently, the stated
sun protection factor (SPF) may not be completely accurate. One
study indicates that actual
SPF's of some sunscreens may vary between 50 percent and 80 percent of their
labeled value. Thus is it best to use screens with SPF of 30 or 30-plus to
insure adequate UVB protection.
Read the labels on sunscreen products carefully, not only to
follow the directions but also to check the ingredients. Some
products contain alcohol and are flammable;
they should not be used near heat, flame or while smoking. These and others
cause burning and stinging when they wash into the eyes. For
some people, one or more
chemical agents in sunscreens cause allergic skin reactions such as burning,
blisters or itching. These side effects are most commonly associated with
PABA and various benzophenones. In addition to their active ingredients,
some sunscreens
also contain fragrances or preservatives that cause allergic reactions. Mango
has recently been added to one brand of sunscreen; for those who are allergic
to mango this product may cause more suffering than a sunburn!
If your sunscreen suddenly does not seem to be working well,
it may be because you are experiencing increased sensitivity
to light. Common agents that can cause
photosensitivity are alpha hydroxy products, nonsteroidal anti-inflammatory
drugs such as ibuprofen and some antibiotics and antihistamines.
Many ingredients in
soaps and cosmetics are potential culprits. Even sunscreens themselves can
cause photosensitivity, especially those that contain PABA or
a benzophenone.
Because of the potential side effects, children should use sunscreens
that contain physical rather than chemical radiation blockers.
Zinc oxide and titanium dioxide
both provide broad spectrum protection, and they are now more transparent
than they used to be, so they look better! These physical blockers
also are recommended
for adults' most exposed areas, such as ears and noses.
So, use sunscreen wisely and don't count on any product to provide
full protection from the sun. Find a tightly-woven shirt (or
the new sunblock clothing), a hat
and a shady spot for midday.
For more information
check out these Web sites—Environmental
Protection Agency, Food and Drug Administration, MEDLINEplus and National
Institutes of Health.
University
Health Services Manoa provides
clinical and educational services for faculty, staff and students
of UH Manoa. |
