Which ingredient inactivates sunscreen?
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free skin care · Sat Jul 30, 2005 7:28 am

Which ingredient is said to inactivate or decrease the efficacy of sunscreen? I would like to do more research on this, as I have read that some foundations contain this ingredient.

Another question: Since I like to have foundation onhand for special occasions, what are some good foundations that do not contain this particular ingredient?

free skin care · Sat Jul 30, 2005 7:40 am

Iron oxides are what you want to avoid with LPR. This means no mineral makeup or tinted SPF products which contain iron oxides, like titanium or zinc. The huge sunscreen thread gives you some more info. I think the iron oxides degrade the Avobenzone (sp) creating free radicals and decreasing your protection. Because of that, foundation with no spf is probably better.

free skin care · Sat Jul 30, 2005 8:00 am

Faith, thank you! You know, on the occasion where I do use foundation, I actually (maybe instinctively) make a point of using ones with no added SPF. Since I wear such a good sunscreen already - Anthélios products - it would just feel odd applying a sunscreen with the insubstantial, flimsy protection they typically provide.

I will take a look at the sunscreen thread you mentioned. Thanks again!

free skin care · Wed Aug 08, 2007 12:59 pm

I know this thread is 2 years old Embarassed

but I didnt want to start a thread knowing its already discussed...but I do want to know more about what ingredients can degrade any sunscreen, be it physical or chemical?

free skin care · Tue Aug 14, 2007 6:25 am

so you are saying adding a swirl of mmu over your sunscreen IF it contains avobenzone will start to break it down.

I don't think mmu would affect mineral based(physical sunscreens) - don't quote me, it's a long time since I took chemistry, I'm sure someone will add something to clarify.

free skin care · Tue Aug 14, 2007 10:24 pm

Eve wrote:

so you are saying adding a swirl of mmu over your sunscreen IF it contains avobenzone will start to break it down.

I don't think mmu would affect mineral based(physical sunscreens) - don't quote me, it's a long time since I took chemistry, I'm sure someone will add something to clarify.

I think you are right, Eve. MMU would ONLY be affected using chemical SS that contains Avobenzone!

free skin care · Wed Aug 15, 2007 1:57 am

you both are right--just remember mineral goes with minerals!

BUT I tend to believe lately that companies that manufacture chemical ss have recently wizened up to these problems. Many 'new and improved' formulations contain avobenzone (stabilized with tinosorbs) AND iron oxides such as for tinted sunscreens. I tested Bioderma's out on the beach in mid-summer and my skin did not tan. It has an spf rating of 50+ and a PPD rating of 35, so it's about as serious of a sunscreen as you can find. It also does not create a greasy film on your skin and makes your skin glow.
I have to admit that out of sheer fear, I do not apply powder or makeup over even this sunscreen, but I'd say that fear is counter-intuitive, knowing the ingredients.
I also think that our sunscreen rules re: avobenzone and MMU are a bit outdated and refer to unstabilized avo ss that aren't even on the market much anymore.

Hopefully the general public will get some more scientifically based information soon...

--avalange

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