Neutrogena just released the results of a sunscreen survey, and I'm a bit disappointed in the results!
While 80% of American agreed that sun exposure is bad, 60% of all Americans reported that they rarely or never put on sunscreen. And if you are using it, only 27% reported using at least 1 ounce of sunscreen, which means no one is using enough! If you don't apply a full ounce to your body, you are definitely under applying.
Under applying means you aren't getting all the SPF you think you are. In fact, if you apply half the dermatologist-recommended one ounce of sunscreen, you get the protection of only the square root of the SPF. So by applying only half-ounce of SPF 70, actually gets you an SPF 8.4.
Finally, they reported that 32% of Americans were concerned about not getting enough Vitamin D due to sunscreen use. While it is true that your body doesn't make as much Vitamin D with sunscreen use, you don't need much exposure every despite appropriate sunscreen use. Actually, you should be getting Vitamin D from other sources, like nutritious food. So, don't forget to drink your milk or take a calcium supplement with Vitamin D if you are concerned.
I have a bunch of sunscreens sitting here that I haven't had time to write about yet with the move, new job, etc. Hopefully I'll be reviewing them soon!