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Broad-Spectrum Sunscreens Block UVA and UVB

Broad-Spectrum Sunscreens Block UVA and UVB

NEW YORK--Sunscreens represent the first line of defense against
skin damage from the sun, and broad-spectrum products offer the
best protection, Madhukar A. Pathak, MB, PhD, said at a media
conference sponsored by the Skin Cancer Foundation.

Commonly available products are very effective at preventing the
acute effects of ultraviolet B (UVB) radiation, but many products
offer no protection against UVA light, said Dr. Pathak, senior
associate in dermatology, Harvard Medical School, and chairman
of the Foundation's Photobiology Committee.

UVB radiation (wavelengths from 290 nm to 320 nm) causes sunburn,
tanning, photoaging, and skin cancer induction, while UVA radiation
(wavelengths of 320 nm to 400 nm) is associated with the immediate
tanning reaction, photoaging, and tumor promotion.

The currently available products (SPF 15 or less) do an excellent
job of preventing sunburn when used properly, but they are unsatisfactory
in preventing tanning, he said. In addition, although sunscreens
provide good protection from the DNA damage caused by low doses
of UVB, it is not yet known how effective they are in preventing
DNA damage at high exposure dose levels.

Current sunscreens do only a fair to good job against the chronic
effects of high-dose UVA and UVB radiation, he said. They will
ameliorate but not necessarily prevent photoaging, sun-related
immunosuppression, and non-melanoma skin cancer.

Possible new sunscreen strategies that might provide better protection
include the use of antioxidants, free radical quenchers, melanin,
and sunscreen-enriched liposomes, he noted, but these are all
in the future.

Dr. Pathak said that the "bottom line" for sunscreen
strength is SPF 15. Any sunscreen with a lower SPF does not provide
sufficient protection. However, he recommends the use of products
with an SPF of 30, because they also provide partial, if not total,
protection from UVA radiation.


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