Comments on: Skin Care Myths: Adding Sunscreens Adds SPF http://thedermblog.com/2008/06/02/skin-care-myths-adding-sunscreens-adds-spf/ Smarter Skin Care Fri, 20 Nov 2009 18:11:07 -0700 http://wordpress.org/?v=2.8.6 hourly 1 By: Choosing Sun Screen http://thedermblog.com/2008/06/02/skin-care-myths-adding-sunscreens-adds-spf/comment-page-1/#comment-8345 Choosing Sun Screen Tue, 30 Sep 2008 07:17:44 +0000 http://thedermblog.com/?p=270#comment-8345 I didn't know this but I suppose it makes sense--the total SPF equals the SPF of the strongest sunscreen applied. But wouldn't weaker sunscreens dilute the stronger one? I didn’t know this but I suppose it makes sense–the total SPF equals the SPF of the strongest sunscreen applied. But wouldn’t weaker sunscreens dilute the stronger one?

]]> By: Caitmin http://thedermblog.com/2008/06/02/skin-care-myths-adding-sunscreens-adds-spf/comment-page-1/#comment-3147 Caitmin Tue, 10 Jun 2008 05:30:15 +0000 http://thedermblog.com/?p=270#comment-3147 I never knew this - thanks. I still like the multi-colored zinc used Australia - at least you can see its still there which is greats when your dealing with kids I never knew this – thanks.

I still like the multi-colored zinc used Australia – at least you can see its still there which is greats when your dealing with kids

]]> By: Richard http://thedermblog.com/2008/06/02/skin-care-myths-adding-sunscreens-adds-spf/comment-page-1/#comment-3108 Richard Mon, 09 Jun 2008 03:06:49 +0000 http://thedermblog.com/?p=270#comment-3108 In general, the above is true. A note about SPF: SPF is on a logarithmic scale; there is a bigger difference between SPF 25 and SPF 30 than there is between SPF 30 and SPF 45. SPFs below 15 are basically worthless. When I am on the water, I apply a sunscreen containing avobenzone, wait a few minutes, and then apply one containing zinc oxide and titanium dioxide. This seems to work well for me: My arms and legs (with just avobenzone sunscreen) get darker while my face (with both) doesn't get darker at all.* *A study has shown zinc and titanium to degrade avobenzone, but the time period was over a week and in aqueous solution. Avobenzone gets absorbed into the upper layers of the skin while titanium dioxide and zinc oxide don't. In general, the above is true.

A note about SPF: SPF is on a logarithmic scale; there is a bigger difference between SPF 25 and SPF 30 than there is between SPF 30 and SPF 45. SPFs below 15 are basically worthless.

When I am on the water, I apply a sunscreen containing avobenzone, wait a few minutes, and then apply one containing zinc oxide and titanium dioxide. This seems to work well for me: My arms and legs (with just avobenzone sunscreen) get darker while my face (with both) doesn’t get darker at all.*

*A study has shown zinc and titanium to degrade avobenzone, but the time period was over a week and in aqueous solution. Avobenzone gets absorbed into the upper layers of the skin while titanium dioxide and zinc oxide don’t.

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