Sunburn and Sun Poisoning
Medical Author: Siamak Nabili, MD, MPH
Medical Editor: Melissa Conrad Stöppler, MD
Truths, Lies, and Sunscreens
Medical Author: Nili N. Alai, MD, FAAD
Medical Editor: Melissa Conrad Stöppler, MD
 What is the best sunscreen
to prevent sunburn?
Overall, the safest and most effective sun-protection products are pure zinc and/or titanium-based sunblocks. These two
ingredients have been around a long time and boast great safety data. The ideal
sunscreen blocks both ultraviolet A and B (UVA and UVB) rays, is stable, doesn't break down in the sun, and doesn't get absorbed through the skin.
Is there any difference between sunscreens and sunblocks?
Physical sunscreens like
zinc oxide and titanium dioxide are sunblocks; they physically (like a brick
wall) block both UVA and UVB rays. Besides these two, all other sunscreens are
chemical-based sunscreens. Chemical sunscreens like oxybenzone, avobenzone, PABA,
etc., are generally colorless and have special ingredients that filter and reduce
UV rays. Not all sunscreens effectively block UVA as well as UVB rays. The
chemical sunscreens break down with sun exposure and may need more frequent
application.
When should I use a sunscreen?
Dermatologists recommend that everyone use
sunscreen of at least SPF 15 or greater every day, year-round. If you plan to be
in the sun more than 20-30 minutes a day, you should wear sunscreen of at least
SPF 30. Even on cloudy days, about 80% of the sun's rays pass through the
clouds. Nowadays, so many moisturizers, lotions, and makeups have sunscreen
built in that it doesn't make sense to use any products that don't contain
sunscreen. It just makes it so mush easier. I recommend, for example, if you
wear any foundation, that there be at least an SPF 15 built in. If not, you may
want to change brands.
What is sunburn?
Sunburn is an inflammation of the skin that is caused by overexposure to
ultraviolet (UV) radiation from the sun. A similar burn can follow overexposure
to a "sun" (tanning) lamp. UV radiation can also damage the eyes, although no
surface burn is apparent.
Can sunburn cause permanent damage?
Yes. Sunburn early in life increases the risk of developing skin cancer later
on. Repeated overexposure to ultraviolet rays can also
scar,
freckle, dry out,
and wrinkle the skin prematurely. In addition, frequent overexposure to
ultraviolet rays can increase the risk of developing eye cataracts and
macular
degeneration, a leading cause of blindness.
What is UV light?
UV light is radiation energy in the form of invisible light waves. UV light
is emitted by the sun and by tanning lamps.
The sun discharges three types of ultraviolet radiation:
- ultraviolet A
(UV-A),
- ultraviolet B (UV-B), and
- ultraviolet C (UV-C).
Only UV-A and UV-B reach
earth. (UV-C does not penetrate the earth's upper atmosphere.)
Although research has long implicated UV-B as the most likely form of UV
radiation to damage the skin and cause skin cancer, recent studies suggest that
UV-A can also be dangerous.
Tanning lamps also produce UV-A and/or UV-B. These artificial rays affect the
skin in the same way as do UV-A and UV-B from the sun.
When and where are UV rays most intense?
UV rays are most intense at noon and the hours immediately before and after
(between 10 a.m. and 3 p.m.), particularly in the late spring, summer, and early
autumn. Although they are less concentrated at other times of the day and year,
UV rays can still damage the skin and eyes - even in the dead of winter and on
cloudy or rainy days.
UV rays also increase in intensity in relation to altitude and latitude. The
higher the altitude, the greater is the concentration of UV rays. Likewise, the
rays are more powerful the nearer the latitude to the equator.
UV rays "bounce" off reflective surfaces - including water, sand, and snow.
Thus, a skier, swimmer, fisherman, or beachcomber may be bombarded with UV rays
from above and below.
Next: What are the symptoms of sunburn? »
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Sunburn (Sun Poisoning)
Dehydration »
What is dehydration?
The majority of the body is made up of water, with up to 75% of the body's
weight due to H2O. Most of the water is found within the cells of the body
(intracellular space). The rest is found in what is referred to as the extracellular space,
which consists of the blood vessels (intravascular space) and the spaces between
cells (interstitial space).
Total body water = intracellular space + intravascular space + interstitial
space
Dehydration occurs when the amount of water leaving the body is greater than
the amount being taken in. The body is very dynamic and always changing. This is
especially true with water in the body. We lose water routinely when:
- we breathe and humidified air leaves the body;
- we sweat to cool the body; and
- we
urinate or have a bowel movement to rid the body of waste products.
In a normal
day, a person has to drink a significant amount...
Read the Dehydration article »
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