Sunscreens & Sun Protection
by Robert Scheinberg, MD
Runners and other outdoors enthusiasts have an increased risk of both premature aging of the
skin (wrinkles, enlarged blood vessels, discoloration) and skin cancers, which can be
disfiguring or deadly.
To keep your skin in as good a shape as your cardiovascular and musculoskeletal systems, you
must avoid ultraviolet light as much as possible. This means:
- Wearing protective clothing (if you hold a garment up to the light and you can't see
through it, the article of clothing is an excellent sunblock).
- Scheduling runs and outdoor activities before 10 a.m. or after 2 p.m. in the fall and
winter, before 10 a.m. and after 4 p.m. during spring and summer (when the sun is stronger and
midday is 1 p.m. because of daylight savings time).
- Applying effective sunscreens daily, especially before prolonged exposure.
Which sunscreen to choose?
You should choose a sunscreen that:
- Protects you from ultraviolet light in the B spectrum (UVB) which causes sunburn and skin
- Protects you from ultraviolet light in the A spectrum (UVA) which causes aging of the skin
(collagen damage) and pigmentation. n Stays on when you sweat or swim (termed substantivity or
- Does not irritate your skin.
- Does not block your pores, causing acne.
For the past few years, sunscreens have been rated according to their Sun Protection Factor
(SPF). This is calculated by determining the ratio of how long it takes to give a subject
wearing the sunscreen a mild sunburn divided by the time it takes the same subject to get the
same sunburn on unprotected skin. If it takes 10 times as long with the sunscreen on, the
sunscreen would be rated SPF 10. However only UVB is tested and the sunscreens are always
applied very heavily in experimental situations so the manufacturers can obtain the highest SPF
for their products.
Do I need higher than SPF 15?
As a practical matter, yes. If it takes a fair-skinned individual about 20 minutes to burn on
unprotected skin, applying SPF 15 sunscreen as heavily as was done during its rating studies
will allow for 20 x 15 = 300 minutes (5 hours) before burning. However since studies have shown
that the average person only applies half to one-third of the sunscreen used in the studies,
and some may be rubbed or sweated off, I recommend SPF of 30 or higher so you have a margin for
error and still have SPF 15 protection.
In addition, I recommend UVA protection with sunscreens containing oxybenzones, cinnamates and
especially parsol 1789 (avobenzone). The base can be alcohol or moisturizing cream or lotion,
depending on the oiliness of your own skin. You should look for sunscreens that are
water-resistant (little decrease in effectiveness after 90 minutes of water immersion) and
noncomedogenic, which means they did not cause blocked pores (comedones) or acne when
If most sunscreens irritate your skin, try sunscreens promoted as chemical free or natural.
These sunscreens use physical blockers such as zinc oxide and titanium dioxide that have such
small particle size that they almost disappear when rubbed into the skin.
Use sunscreen every day, whether you think you are going to be out in the sun or not. Recent
studies correlating increased sunscreen use with increased numbers of skin cancers did not take
into consideration skin type!
Fairer-skinned persons are more likely to get skin cancers than olive or black skinned
individuals. Fair-skinned persons also tend to use sunscreens more often. Many of them were
badly sunburned during their youth, initiating the skin cancers years before they became
visible. This tendency to sunburn is why they wear more sunscreen during adult life, when the
skin cancers appear.
If you compare people with equivalent skin color, users of sunscreen are younger looking and
have fewer skin cancers than non-users. However, even darker skinned people can get skin cancer
and very frequently get leathery, "weathered" skin from chronic sun exposure even if
they never burned. They, too, should wear sunscreen daily, the higher SPF the better.
If you find the most effective sunscreens too heavy to use every day, I suggest you apply
moisturizer containing SPF 15 sunscreen every morning and apply waterproof SPF 30+ sunscreens
20-30 minutes before running or swimming.
It is important not to wipe off sunscreen when toweling down or wiping away perspiration. Pat
your skin dry instead of rubbing. If sunscreens sting your eyes, try to use a waxy lip
sunscreen on your eyebrows and pull your hat down over your forehead to act as a physical
sunblock. Apply sunscreen on the nose and from the sides of the eyes downward, not forgetting
the ears, back of the neck, arms, hands and legs.
Remember that the most effective sunscreen for you is the one you wear daily rather than the
one with the highest SPF that you leave in your medicine cabinet.
Dr. Scheinberg is a clinical professor of dermatology at UCSD Medical Center and
maintains a practice at the Dermatologist Medical Group of North County, Inc.