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What's an SPF?

Many of the sunscreens that you see on the shelf have a number on them, called an “SPF.” What does SPF stand for?

  1. Skin Penetrance Factor

  2. Skin Pleasantry Factor

  3. Skin Protective Factor

  4. Sun Penetrance Feature

  5. Sun Protective Factor

The correct answer is (e), Sun Protective Factor. This number measures the effectiveness of that sunscreen in protecting you from a sunburn from either sunlight, or from ultraviolet light (UV light) from tanning bulbs.

So generally a higher SPF means a better sunscreen. If it takes you 10 minutes of mid-day sun to turn pink from the sun, with an SPF 6 you could be in that same sun light for 6X10 minutes, or 60 minutes (1 hour), without turning pink, or with an SPF 10 you could be in the sun for 10X10 minutes, or 100 minutes, without turning a pink color.

The problem with the SPF concept is that it doesn’t look at the full harmful effects of UV light on your skin, which include not only sunburn, but also skin cancer and premature wrinkling of your skin. So you want to look for a sunscreen with a high SPF that is also labeled as “Broad Spectrum,” meaning that it protects against both the traditional UVB rays, but also the now-known-to-also-be-dangerous UVA rays.

If you have a skin growth with changes of color or size, by all means get it checked for skin cancer or melanoma. The photo above shows a melanoma, the deadliest type of skin cancer. My own Dermatology practice – with Rheumatology and Dermatology Associates ( – is in Cordova TN – but you can find a Dermatologist close to you by going to the American Academy of Dermatology web site,, then simply plugging your zip code into the “Find a Dermatologist” tab. Remember that early detection definitely saves lives.

PS: a personal sunscreen favorite of my own is Vanicream Sunscreen Sport SPF 35, now available from, a company of which I am President (4 oz: $17.95 plus tax). Vanicream is appealing because it’s broad spectrum, but also fragrance-free, and being water-resistant, it’s less likely to run into your eyes, always a concern with products you are going to be using on your face.

Big River also manufactures an anti-wrinkle cream – GlycoShea™ Facial&Neck Cream – with an Alpha-Hydroxy Acid – Glycolic Acid. Check it out!

George Woodbury Jr. M.D.

Board-certified Dermatologist and President of Big River Silk Skincare Inc.

8143 Walnut Grove Road

Cordova TN 38018



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