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Exposure to the sun can cause both acute and chronic injury to the skin.
The acute injury is sunburn. Chronic effects include degenerative changes
such as wrinkling, aging, pigment alterations, decreased immune reactivity
of the skin, pre-malignant lesions and malignant tumors. Those who have
had total body irradiation have an increased sensitivity to sun injury
and to changes in skin pigmentation. For these reasons alone, we suggest
that those who have undergone a bone marrow transplant with total body
irradiation avoid significant contact with the sun.
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Most typical sunscreens contain ultraviolet light absorbing chemical agents
in a cream, oil, lotion or gel vehicle. The most widely used chemical sunscreens
contain para-aminobenzoic acid. ultraviolet light is the major cause of sunburn.
The results of experiments in small animals indicate that effective sunscreens
can prevent skin cancer, but chronic changes can occur in human skin exposed
to sunlight even when the skin is effectively protected against the redness
caused by a sunburn.
Most manufacturers of commercial sunscreens now specify the sun protection
factor (SPF) of their products on the label. The sun protection factor is the
ratio of the time required to produce redness through a sunscreen product to
the time required to produce the same degree of redness without the sunscreen.
All sunscreens should be reapplied after swimming or sweating. Patients should
be warned, however, that the application will not extend the period of protection.
Many chemical sunscreens can themselves cause reactions with sunlight and the
skin. Occasionally some patients are allergic to the chemicals within the sunscreen.
Every 1,000 foot increase in altitude adds 4% to the intensify of redness producing
ultraviolet light. This means that at 5,000 feet above sea level such as in
the city of Denver, the intensity of sunlight is 20% greater than at sea level.
Fresh snow is a very effective reflector as are white painted surfaces or sheets
of aluminum. Reflection from water is variable but unless the sun is directly
overhead, the reflection from water is only a small percentage of ultraviolet
radiation. Sand reflects about 25% of ultraviolet radiation which is probably
why people get a better tan while they are at the beach. Reflected light can
be especially damaging because it may strike the skin in previously unexposed
areas.
On a bright, clear day, redness of the skin can develop due to reflected and
scattered sunlight, even in the shade or under an umbrella or a hat, particularly
near snow or white sand. A bright day with a thin cloud cover has at least 60-80%
of the ultraviolet radiation present. However, since the skin may be cooler
on a cloudy day, some people may not feel hot and therefore may over-extend
their exposure to the sun.
As much as 96% of ultraviolet radiation can penetrate clear water, especially
when the sun is not directly overhead. This means that you can get sunburned
while in a pool. Tightly knit, dry clothing stops almost all ultraviolet radiation,
but wet or loosely knit clothes may permit some of the radiation to penetrate.
Listed below is a sampling of some of the sunscreens which are currently available.
You will note their sun protection factor. This is only meant as a sampling
of those that are available; it is not meant to indicate that these are the
only acceptable sunscreens. A generic sunscreen with a sun protection factor
of 15 or greater is quite acceptable.
Acceptable Sunscreens
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Sun Protection Factor
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Product Name
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20
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Aramis SPF20 Sun Protection
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19
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Clinique SPF19 Sun Block
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15
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Elizabeth Arden Sun Blocking Cream
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15
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Bain de Soleil, Ultra Sun Block 15
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15, 30
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Coppertone Sunblock Lotion
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8, 15, 30, 48
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Coppertone Sport
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40
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Coppertone for Kids
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30, 45
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Coppertone Water Babies
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15, 30, 50
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Banana Boat Sunblock Lotion
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