Monday, March 22, 2010

SPF - what exactly does that mean?

What is sun protection factor or SPF? How is it defined? SPF is defined as...
the dose of UV radiation required to produce 1 minimal erythema dose (MED) on protected skin after the application of 2 mg/cm2 of produce divided by the UV radiation to produce 1 MED on unprotected skin.

In other words, it's how much of this stuff you need to use to protect your skin from a dose of radiation that would affect unprotected skin. The higher the number, the more protection you should get.

"Water resistant" sun screen must maintain its SPF after immersion in water for 40 minutes.

"Very water resistant" sunscreen must maintain its SPF after immersion in water for 80 minutes.

Broad spectrum or full coverage sunscreen will protect against both UVB and UVA rays.

So why do we care about sunscreen? Because it is one of the key things you can do every single day to slow down the photo-aging process (join me tomorrow for that topic...)

And please don't make your own. There are so many factors that go into making sunscreen and we can't test it to make sure it is effective! (If you are interested in learning more, this is a great PDF on the topic. So much to think about!)

1 comment:

Anonymous said...

Thank you (again and again) for taking time on this blog.. great information.
BTW - the BEST sunscreen i've ever used i bought in Canada (and Europe). LaRoche Posay Anthelios. I can use this and go out in our sun (desert southwest) for long periods of time and not burn. Wonderful stuff. I stock up whenever i can.