Isomers 101: Sun Protection Factor (SPF)

0 add a comment

Sun Protection Factor (SPF) is a simple scale for rating sunscreens. SPF products usually range from 8 to as high as 60. These numbers refer to the product's ability to screen UVB rays which are responsible for the sun's burning effects or erythema (redness).

The SPF scale / rating is measured by determining the required amount of time needed to induce a sunburn on protected skin to the amount of time needed to produce a sunburn on unprotected skin.

For example a fair-skinned individual’s skin usually suffers from erythema after 10 minutes of exposure to sun’s UVB rays. Ten minutes is now the "initial burning time." Now application of a SPF 2 product should allow the same individual to stay out in the sun for 20 minutes before he / she suffers from erythema.

If the same individual now uses a SPF 20 sunscreen it should take him approximately 200 minutes (~ 3 hours) to suffer from erythema.

Application of an SPF 60 will change this number to 600 minutes; or simply 10 hours! Now here is the issue. Do you know anybody that can stay in the sun for 10 hours without perspiration! Because once you start sweating or swimming the sunscreen will start to wash away and is no longer protecting the skin in the same manner.

In my opinion it is best to use a SPF range of 20-30 and reapply a fresh layer of the product every two to three hours.

Share this post


No comments at this moment

Leave a Reply