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What do I need to know about sunscreen?

Sunscreens are an important component of a person’s fight against skin aging and skin cancer.  There are plenty of misconceptions and misinformation about sunscreen that are passed along from one person to the next.  Considering that 90% of skin aging and cancer is due to cumulative sunlight exposure, protecting the skin from the sun’s harmful rays is critical in preserving one’s cutaneous health.  For most people, having a sunscreen that isn’t sticky, irritating, acne-causing, greasy or laced with perfumes goes a long way towards consistently using it.  Sunscreens function by either reflecting the ultraviolet (UV) rays or absorbing sunlight and transferring that energy to heat.  There are two types of UV rays:  UV-A rays and UV-B rays.  UV-A rays cause skin aging and are present from 6 am to 6 pm year-round.  They penetrate car window glass and reflect off concrete and water.  Since they have a long wavelength, they cause collagen damage deep in the skin.  According to recent FDA rules on sunscreen, any product that claims “broad-spectrum” must protect against UV-A rays.  The SPF number does NOT tell you how well the product protects against UV-A rays (only UV-B), however.  Zinc oxide and titanium dioxide, both FDA approved ingredients, provide the best protection against UV-A rays (although a formulation that isn’t tinted will leave a white hue to the skin when applied).  Organic sunscreen ingredients, such as oxybenzone and avobenzone, tend to sting the skin/eyes and are prone to causing allergic reactions similar to poison ivy.  UV-B rays peak at noon time and are strongest during the summer months.  In fact, two-thirds of the day’s UV-B rays are emitted in the window between 11 am and 2 pm.  UV-B rays are responsible for sun burns and skin cancer and less with skin aging.  The Solar Protection Factor (SPF) is a measure of a sunscreen’s ability to filter UV-B rays (not UV-A rays).  A common misconception is that a super high SPF provides a lot more protection than a lower one.  In fact, SPF 15 filters about 93% of the harmful rays, SPF 30 about 95%, and SPF 100 97% (think law of diminishing returns).  Since the higher the SPF the thicker and greasier the product, Dana Point Dermatology recommends an SPF of 30.  Another myth is that a sunscreen remains active until you wash it off.  This is incorrect because once a particle of sunscreen absorbs light, it can’t be used again.  This is the reason sunscreen must be reapplied after 2 hours of sun exposure.  Another common myth is that rubbing a sunscreen on the skin promotes complete protection.  Make sure to use plenty of sunscreen per application--a quarter-sized amount for the face and neck.  Spreading it too thinly will drastically reduce the SPF number delivered to your skin, setting up a false sense of security.  Although zinc oxide and titanium dioxide offer the best protection on the market, there are still wavelengths of sunlight that slip through.  This is the reason why covering up, seeking shade and avoiding the sun during 11 am to 2 pm are crucial for an overall sun protection strategy. 

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