Beauty Questions? Ask Dr. Irwin
- Sun Protection 101

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Reader’s Question

Dear Dr Irwin,

I would like to ask about sun protection:
1) What is the difference between UVA and UVB rays, and is one more detrimental to the skin than the other? How do we know if we are exposed to more UVA or UVB rays? (e.g. does it depend on seasons or weather, or being indoors or outdoors?)
2) I have heard of chemical sunscreens and mineral sunscreens, what is the difference? Is any one more superior to the other?
3) Regarding SPF, is it that a higher SPF offers MORE EFFECTIVE coverage (i.e. against stronger sun’s rays) or longer HOURS of coverage?
4) If one is working indoors most of the time (or outdoors, whichever is the case), is there any difference in the type of sunscreen one should be using/purchasing (e.g. look for different types of ingredients in the sunscreen)?

Thank you.
Polly

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Dr. Irwin’s Answer

1) What is the difference between UVA and UVB rays, and is one more detrimental to the skin than the other? How do we know if we are exposed to more UVA or UVB rays? (e.g. does it depend on seasons or weather, or being indoors or outdoors?)

UVB is a shorter ultraviolet wave than UVA.  UVB damages the outer layer (the epidermis) more whereas UVA travels deeper into the skin (the dermis) and damages the deeper layers more.  Both UVA and UVB are rays of natural light which you are exposed to everything time you are outdoors. Please see: http://www.skintour.com/skin-care-products/sunscreens.

2) I have heard of chemical sunscreens and mineral sunscreens, what is the difference? Is any one more superior to the other?

Chemical sunscreens work by binding to the cells themselves and mineral sunscreens work by providing a barrier of invisible protective particles that bounce light back so UV waves won’t penetrate the skin.  Generally, mineral sunscreens in the right percentages are superior because they don’t degrade as much in exposure to light.

3) Regarding SPF, is it that a higher SPF offers MORE EFFECTIVE coverage (i.e. against stronger sun’s rays) or longer HOURS of coverage?

The FDA is coming out soon (probably 2012) with the requirement that products have an SPF (which we have now and only refers to the amount of UVB coverage) as well as a # that will explain the amount of UVA coverage (which is more easily said than done).  Look for sunscreens that are at least SPF 30 and that say ‘broad spectrum’.  Best are sunscreens that contain 5-20% zinc which blocks both UVA and UVB — and the higher the percentage the better.

4) If one is working indoors most of the time (or outdoors, whichever is the case), is there any difference in the type of sunscreen one should be using/purchasing (e.g. look for different types of ingredients in the sunscreen)?

If you work indoors, you aren’t exposed to UVA or UVB unless you have a desk near a window. UVA goes through window glass, which includes your car windows and windshield unless you have put in special window protection. Here is a list of sunscreens I recommend : http://www.skintour.com/sunscreens

Best,
Dr. Irwin

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