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Sunscreen Options and Sun Protection Factor (SPF)

By Sherry Beames, La Crosse Wellness Department

Finally, the sunshine has arrived to the Midwest.  With it, come many questions about sunscreens and their usage.  Sunscreen is divided into two types, Physical and Chemical.  Physical sunscreens contain minerals, like Titanium Dioxide or Zinc Oxide, which provide a barrier that reflects UV rays away from the skin.  Chemical sunscreens contain organic chemical compounds, such as Octocrylene, Avobenzone, Homosalate, and Octinoxate, which absorb the UV rays and before they penetrate the skin. Ultraviolet A rays (which may cause photoaging and skin cancer) and Ultraviolet B rays (sunburn causing) are both harmful to skin with prolonged exposure.

What does that mean?  Here are some advantages and disadvantages of both types of sunscreen.

Physical sunscreen advantages: 
• Offers broad spectrum protection (UVA and UVB)
• Works immediately upon application
• Nonirritating for sensitive skin, such as infants and children, those with rosacea or redness (by deflecting heat), and acne prone skin (its less likely to clog pores)
• Lasts longer in direct UV light
• Most are biodegradable and not harmful to marine ecosystems

Physical sunscreen disadvantages:
• Leaves a ghostly white glow on skin (check out newer items which have added tint)
• Can be thick and hard to apply
• Must be applied generously to get full coverage

When using a Physical sunscreen, choose one with non-nanoparticles, this ensures the particles are not absorbed into the skin and also keeps the barrier between you and the sun thicker.

Chemical sunscreen advantages:
• Thinner in consistency, therefore easier to apply
• Can offer a consistent coverage against UVB rays, double check that it protects against UVA rays

Chemical sunscreen disadvantages:
• Can irritate skin
• Unless stabilized, Avobenzone breaks down quickly  in  UV light
•  Must be applied 15-30 minutes prior to sun exposure

What about Sun Protection Factor?  SPF is a measure of how long you can stay in the sun before you start to burn.  SPF measures UVB rays only, there is no current measure for UVA rays.  This is what the numbers mean:
• SPF 15 blocks 93% of UVB rays
• SPF 30 blocks 97% of UVB rays
• SPF 45 blocks 98% of UVB rays

No sunscreen will block 100% of UVB rays.  Water resistant, or active sunscreen can protect during physical activity or swimming for 40-80 minutes before needing reapplication.  Read the label to be sure.  Application is key.  You must apply enough!  Use 2 Tablespoons for an adult body.  Reapply every two hours, more if you are swimming or active.  For example, four adults at a beach for four hours would use one bottle of 8 ounce sunscreen.  Don’t forget the sensitive areas of lips, feet, and tips of ears.

The best sun safety is to be smart in the sun.  Seek shade when you can, cover up, wear a hat and/or sunglasses, and drink plenty of water.  Enjoy these days while they last!