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Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, research has shown that the best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, and rubbing.[1]
However, more recent research at the University of California indicates that sunscreen needs to be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from the absorbed chemical.[2]
A significant reduction in sun exposure inhibits the production of vitamin D. However, excessive sun exposure has been conclusively linked to some forms of skin cancer and signs of premature aging. Season, geographic latitude, time of day, cloud cover, smog, skin type, and sunscreen all have an effect on vitamin D production in the skin, but fifteen minutes per day of direct exposure to the sun is a generally accepted guideline to follow for optimum vitamin D production.
Experts generally recommend taking a fifteen minute walk in the morning or evening without wearing sunscreen to meet this
Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from the absorbed chemical.[
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Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, research has shown that the best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, and rubbing.[1]
However, more recent research at the University of California indicates that sunscreen needs to be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from the absorbed chemical.[2]
A significant reduction in sun exposure inhibits the production of vitamin D. However, excessive sun exposure has been conclusively linked to some forms of skin cancer and signs of premature aging. Season, geographic latitude, time of day, cloud cover, smog, skin type, and sunscreen all have an effect on vitamin D production in the skin, but fifteen minutes per day of direct exposure to the sun is a generally accepted guideline to follow for optimum vitamin D production.
Experts generally recommend taking a fifteen minute walk in the morning or evening without wearing sunscreen to meet this
Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from the absorbed chemical.[
这条挺吓人的
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