Confused about SPF ratings in physical / mineral sunscreens

Hi everyone - this is my first post on this forum - feel lucky to have found you.

One of the things I've noticed lately is that sunscreens' SPF ratings "seem" all over the place by looking just at the active ingredient concentrations. For example:

Titanium Dioxide 4% and Zinc Oxide 6% 
rated at 50+ (Avene Face & Body)

Titanium Dioxide 5% and Zinc Oxide 10% 
rated 30+ (Blue Lizard Sensitive)

Titanium Dioxide 2% and Zinc Oxide 17% 
rated 30 (MDSolarSciences Mineral Creme)

What am I not understanding or taking into consideration? Is it the inactive ingredients that could be making the difference in the SPF rating?

Can we trust SPF ratings? Or should we ignore ratings and always look for high concentrations of Zinc Oxide (how high is "enough") and Titanium Dioxide (how high is "enough"?)

I am referring only to physical sunscreens because those are the only ones I try to use (I like that they scatter the rays rather than letting them through...wish I could find one that does not leave a white cast though...or leave you greasy...)



  • Excellent question! My guess is that some companies under-report their SPF. (It's always better to underrate rather than over rate.) That could explain some of these differences. The other ingredients can make a difference in the formula. 

    Try a micronized physical sunscreen if you want to get away from the white cast. 
  • FYI, I think mdsolarsciences changed their rating to spf 50. I have noticed this too! If you want one matte with a light tint, try skinceuticals physical fusion. Very matte. I actually found it drying.
  • Thanks Randy!

    When I went to the post that sarahf linked to, the author actually talked about this too...she says that lower levels of active ingredients like Zinc Oxide or Titanium Dioxide likely means the ingredients are micronized...but as far as I can tell she's not a doctor or chemist, even though she seems very knowledgeable. Would you agree Randy that is a likely explanation? 

    And speaking about micronized, I read in one of your comments that you said micronized doesn't always = that it will penetrate the there a fairly quick/easy way to determine whether a micronized sunscreen would protect yet *not* penetrate the skin?

  • sarahf, mdsolarscienes has 3 sunscreens, 2 are SPF 30, 1 is SPF 50 (I own all three).

    See, that's the that my skin is older, it doesn't like to be matte...I want *more* moisture, just not a shiny/greasy look, you know? That doesn't look good either.
  • Ginan: To my knowledge there is no scientific consensus saying that any of these ingredients pose a danger from penetrating skin. If there was such data the ingredients wouldn't be allowed as over the counter drugs. 
  • Yes, you are correct Ginan--I stand corrected.  Weird.  But still, try the skinceuticals.  You might like it.  A lot of people love it, just my skin finds it drying.
  • You can get a free sample if you live near a Blue Mercury store (or you could probably request one on line).
  • OK - that's good to know I don't need to worry about micronized ingredients.

    So do you agree that if Zinc or Titanium is micronized it would require less of it to yield similar SPF to non-micronized? 

    sorry if I'm beating this topic to death - I'm kind of a sunscreen / want to protect my skin nut, and lately I just don't feel confident with SPFs :/

  • Randy--I have a question.  Paula contends that this product does not moisturize your skin with the silicone base it has.  I agree with Gina(n), I find it greasy, so much so that I feel I could skip moisturizer underneath it and just use it as a makeup primer on its own.  I got a sample of it at Sephora (yes, I know, I'm going crazy with products right now...) Is Paula right?
  • edited June 2015
    sarah, for me, none of the mdsolarsciences are moisturizing - and I notice that if I wear them for a few days in a row, my skin starts to look drier (I don't often do this because this sunscreen is expensive!)

    What I usually do - because I actually *do* love the finish on these sunscreens, even though they are slippery - is moisturize my skin well underneath. skin may be drier than yours and able to tolerate it. For me the finish is NOT greasy with these sunscreens - a little tiny shiny, a little slippery (although I cut that down by rubbing it in well and waiting 20 minutes if I can before putting on foundation) - but not greasy.

  • Gina--is your name Gina?  For reference, I find that the mdsolarsciences tinted sunscreen plays really well with Benefit's Hello Flawless powder, which takes down the shine.  In case you're curious to try that one.
  • One could certainly argue that this product is not as moisturizing as other comparable lotions because 1) it doesn't contain water and 2) the main occlusive agent is dimethicone which is a good skin protectant but does not reduce TEWL as much as, say, petrolatum. 

    Is she actually right? I don't know. Someone would have to show TEWL (Transepidermal Water Loss data) comparing this product to a suitable control.  
  • Thanks, Randy! :)
  • edited June 2015
    sarah (yes, you can call me gina :) I own all 3 mdsolarsciences sunscreens - including the tinted one. I do use it once in a while and it's probably my favorite of the tinted sunscreens (I realized today I should make a list of all the sunscreens I tried! Otherwise I'm bound to run into them again, forget I tried them, and order them again :/ today I "ran" into Green Screen in my drawer and I didn't at all remember I had tried that one...)

    I've also been getting away from wearing SPF 30 and wanting to wear only SPF 50 - I really want to keep those UVA rays off my skin.

    But this whole issue of SPF ratings and how all over the place they are with the actives content makes me question SPF ratings...but may just be due to not understanding the technology (e.g., micronized). That's why I'm really hoping Randy can give me *some* reassurance that yes a sunscreen can have have low levels of ZO and TD and still provide the full SPF rating it says...because of course lower levels mean less white cast. 

    I might also write the manufacturers of these sunscreens...but in the past, when I've reached out to companies with questions about their specific ingredients I don't find the customer service reps to be that knowledgable.
  • I wouldn't get too hung up on spf ratings, because they only reflect UVB coverage, not UVA.  I tend to look for a sunscreen with at least 5% zinc oxide, the more, the better.  And you can't beat MDSolarsciences with 17%.  So I wouldn't worry if it says spf 30 on the package--that's only the UVB coverage.
  • Isn't there supposed to be a rating system for UVA coverage?  Wasn't that in the works?
  • Gina, do you find the mdsolarsciences hard to spread?  I find it very hard to see where I've spread it.  I can only tell by feeling my skin and seeing if it has a slippery feel.  But even then, I'm not sure that area is covered because I can't see it going on.  Weird.
  • The other thing I hate about mineral sunscreens.  By the end of the day, either powder foundation or tinted moisturizer applied over the top of them gets cakey and weird, like the zinc oxide particles have wandered into it.  It looks totally wrong and terrible, and I can't see that until I get home where the lighting is better than the bathroom at work.  For me, the only thing that goes on and stays looking reasonable all day over mineral sunscreens is a true liquid foundation.
  • OK - at least the 5% zinc oxide gives me a minimum to look for.

    And yes, that's why lately I've been looking to the solarsciences in my drawer more and more - I trust and love the 17% for my face.

    Thanks for the reminder that SPF only addresses the UVB factor and not UVA - I never actually "connected" that in my mind - all the more reason to look for high zinc oxide content...since part (OK most) of the reason I wear sunscreen is to prevent as much photoaging as possible.

    I didn't know there was a UVA rating in the works like the PA...that would be awesome (and long overdue).
  • I don't find the mdsolarsciences sunscreen hard to spread at all (I'm talking about the SPF 50 one - it's the one I've been using lately)...but...I am generous with the application and there's no doubt in my mind I've covered every inch of skin...

    I don't wear powder foundations (too dry "feeling" for me at this age - I want moisture in *everything*) and tinted moisturizers do nothing for me (same dislike I have for tinted sunscreens - staining and having the neck always somewhat whiter) - so I can't attest to that...but in general I feel like it's hard to find the perfect sunscreen much less sunscreen that looks good with foundation on top...

    One thing that happened to me the other day that was really unpleasant was I wore a mineral sunscreen that was supposed to be water resistant to 80 minutes to the gym and it was pooling and coming out of my pores halfway through my workout. :/
  • Thanks, Gina!  See, the spf 50 one is white, so that could make it easier to see as you spread it than the tinted one, which just disappears into my skin.  But I prefer it tinted because it gives me options for layering over it and also because I think it has less of a tendency to kind of leech into, or affect the color of, products I put over top of it than the white ones.
  • And yes, when I sweat, the mineral sunscreens do that on me, too.
  • Also--take what I say with a grain of salt about 5% or more.  That is just my take on what you need for reasonable UVA coverage.  What I can say is that 17% is on the high end relative to products on the market that I've seen (and used).
  • Sarah - tomorrow I will make it a point to wear the SPF 30 one and get back to you on whether I find it hard to spread - I have both the tinted and untinted - I'll try the tinted first since I know that's the one you're wearing most (actually not even sure you own the untinted one).

    I never tried the tinted under a foundation - that may be an interesting thing to try especially because the SPF 50 shows white even through foundation - had never occurred to me to try that.

    OK thanks for pointing out the 5% is not based on any specific "scientific" thing - I really appreciate that - it gives me something to work with though. And yes 17% is awesome.
  • Thanks, Gina.  Curious to hear your take on the tinted one.  Re: 5%  Here is a link that backs me up, but not sure what their sources are.  I've just generally felt that concentrations below 5% are too trivial, but not sure where I first heard that or if I made it up...
  • Also, here's an article where they compare 3% avobenzone (a pretty standard concentration) to 5% zinc oxide.
  • edited June 2015
    And another link--but not sure what her sources are.

  • edited June 2015
    OK - so...I used the tinted solarmdsciences yesterday - I had totally forgotten what it felt like and looked like. 

    Definitely harder to spread than the SPF 50 one - it doesn't feel as "slippery" - it's more liquidy so the consistency makes it not go as far...the consistency reminded me a little bit of the foundation I usually wear the Estee Lauder Double Wear - you have to work kind of fast. For reference, I only moisturized my face with CeraVe Baby Lotion and not with the SkinActives Every Lipid Serum I usually use (which is a blend of lipids that is somewhat oily/slippery. Just to not give it any help.

    So yes I had to be more conscientious that I was covering every spot.

    I am so glad I did this - I had forgotten just now *nice* the tinted one is - it is the most natural I've seen so hardly any white cast AT ALL...and a matte finish...reminded me why I like this brand - I feel like for the most part, they've nailed the finish and consistency. Not saying their sunscreens are perfect in every situation (the SPF 50 one can be greasy feeling especially under foundation) - but pretty damn good.

    I'm running low on all 3 and I will probably reorder them all, including the tinted one now! (thank to this conversation with you).
  • Thanks for all this links! Will check them out...let's see if I arrive at the same conclusion / feeling you did about 5% ZO.
  • I'm not sure I'm happy with the finish/consistency.  To me, it's just feeling too oily and looking too shiny.  It's funny how different people's skins react so differently.  But I want to like it, because of the high coverage...what to do...
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