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Fri Jun 27, 2008 9:50 am  |
Hi
I wonder if anyone here can explain why this is happening to me. I apply the Anthelios Pediatrics spf 50 sunblock everyday. It's alright, a bit shiny, a little too metalic and reflective but I suffer for the great PPD protection it gives my combination face.
I apply foundation very lightly and then powder. I have to powder because of the natural oils in my t-zone and the grease from the sunblock. When I'm done, I often assess that some areas look a little too powdery, especially above the lip and that little area a cm below the iris. So I set about trying to make it look moist there. A touch of Anthelios won't cut it - the metallic, reflective problem, you see. Then I discoved a little sample I had from Avene, spf50. Brilliant, great texture, better than Anthelios for me to be honest. So I put a little on the top of my lip and under the eye area. It's been quite hot here in the UK and what's happened??? My face feels burnt above my lip area. Grrrr. Why oh why has this happened?
Is Avene simply not as effective or longlasting as Anthelios or do they cancel each other out in some way?
If I trusted Avene protection more I would use the tinted spf 50 and forgo the Anthelios completely as I much prefer the texture and the peachy tint is very flattering and allows less foundation. I don't think the PPD is as high as Anthelios and now this has happened I do doubt its effectiveness. I also notice that the Avene recommends re-application every 2 hours!!! What planet are they living on for a busy woman to be able to do that all the time???
Anyone else compared the two brands? I'd love to know. |
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Fri Jun 27, 2008 10:34 am |
Hi Camelia, I never tried the Anthelios sunscreen myself as I can tell that it's quite thick & greasy.
I tried the Avene SPF 50 (non tinted) version. I think mine is an older version. It's not the orange tube one. It's a thick pasty white cream. I'm quite fair skin myself but it makes me look like a ghost. Also, I feel my skin is suffocating like it cannot breathe cuz it's so thick & heavy. I applied the suggested 1/4tsp to my face... It might be better if I applied less but that'll defeat the purpose of adequate sun protection, right?
I guess when they suggested to reapply every 2hrs, it's more like for those that're under the direct sun for a long period of time such as when u r at the beach or something. I personally think it's not really necessary to use a heavy duty ss on a daily basis if you're mostly indoors and perhaps out in the sun for a few minutes and back. I think SPF 30 or a PPD of around 10 for daily use is good. If you're going to spend hrs out in the sun, then of course something higher is better.  |
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Fri Jun 27, 2008 10:47 am |
Hi Stardustdy
Yes, the Avene formulation has definitely changed since then. This wasn't thick, pasty nor white but a lighter, peachy, pretty shade in the orange tube.
I hear what you're saying about the lower spfs having better textures. However I remember reading a report a couple of years ago from a dermatologist saying that if you apply foundation and powder on top of sunblock, the protection is dramatically reduced. It's only logical that if one is applying another substance over the top (even if you wait 20mins after application) that the action of rubbing in the foundation and blotting with powder will reduce the potency of the sunblock. If I recall correctly it said something like an spf50 will be reduced to that less than half with the application of cosmetics. I wish more cosmetics would have UVA/ppd in them.
What I'm really intrigued to know is whether the Avene and Anthelios ingredients fight each other in some way???? |
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Fri Jun 27, 2008 10:50 am |
Is this the Euro version with Tinosorb? If so, I'd be surprised if it caused you to burn, since it is pretty effective for both UVA and the burning UVB rays. Here are two other guesses: perhaps you missed a spot in application--that happened to me once and I ended up with a painful and embarassing pink spot!! Or, even more likely, perhaps you are sensitive to an ingredient in the Avene sunscreen. The area around the lips is particularly sensitive for me, and I find that I sometimes suffer ill effects there from products that are otherwise OK for me.
Hope you recover quickly and figure out what is causing the problem. |
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Fri Jun 27, 2008 11:05 am |
Hi Flitcraft
I'm baffled by this too. I couldn't have missed a patch because if you saw the way I apply Anthelios, you'd be in no doubt, I continually amazed that my skin can even breathe through the stuff! I applied the Avene over the Anthelios and powder in a small, concentrated area.
I think you may be right about the top of my lip being sensitive. I guess I'm lucky in that I never have to bleach that area or remove hair from there so it shouldn't be sensitive but if I occasionally use too much bleach when cleaning the bathroom (which isn't often!!), I do get a sensitive, burnt sensation above my lip so perhaps it's just an over reactive area there for me. I some pigmentation there so I hate a burnt feeling for fear that it might get worse.
My reasoning for it was that there might be more physical ingredient in the Avene than the Anthelios and that was fighting the chemical of the Anthelios and reducing the overall protection somehow? I could be completely wrong. |
_________________
Medium toned , oily skin, lover of sunblock and anti-ageing products & supplements. On a perpetual quest for the perfect v. high PPD, non greasy sunblock! |
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Fri Jun 27, 2008 11:20 am |
Cameilia, I know that Zinc & Titanium Dioxide will degrade Avobenzone. So perhaps u can check the ingredients to see.
Yeah I know applying makeup over ss will decrease its effectiveness but it's hard not to blot with powder on top if you need extra coverage or just to make it look not too shiny. That's why I applied MMU on top cuz there's sun protection. Although it's not much but better than nothing  |
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Fri Jun 27, 2008 12:16 pm |
| Stardustdy wrote: |
Cameilia, I know that Zinc & Titanium Dioxide will degrade Avobenzone. So perhaps u can check the ingredients to see.
Yeah I know applying makeup over ss will decrease its effectiveness but it's hard not to blot with powder on top if you need extra coverage or just to make it look not too shiny. That's why I applied MMU on top cuz there's sun protection. Although it's not much but better than nothing |
To cover all bases, you can apply mineral make up on top of a physical sunscreen. Now I'm starting to powder my oilier areas with mineral makeup over my sunscreen and I'm really happy with that. |
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Fri Jun 27, 2008 1:00 pm |
| But doesn't mineral sunscreen degrade much faster than a chemical one with the more stable Mexoryl? |
_________________
Medium toned , oily skin, lover of sunblock and anti-ageing products & supplements. On a perpetual quest for the perfect v. high PPD, non greasy sunblock! |
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Fri Jun 27, 2008 1:04 pm |
| Camelia wrote: |
| But doesn't mineral sunscreen degrade much faster than a chemical one with the more stable Mexoryl? |
Mineral sunscreen does not degrade at all. I think you're thinking of something else- mineral sunscreens can cause some chemical sunscreens to degrade. However, if you just stick to physical (mineral) sunscreen you're totally safe. |
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Fri Jun 27, 2008 1:14 pm |
| Aahh, interesting... So what is it that puts off so many from using a physical sunscreen? Why do the large companies like L'Oreal use so many 'chemical' components in their sunscreens. What is the highest PPD of a physical sunscreen? Thanks for this information! |
_________________
Medium toned , oily skin, lover of sunblock and anti-ageing products & supplements. On a perpetual quest for the perfect v. high PPD, non greasy sunblock! |
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Fri Jun 27, 2008 1:35 pm |
| Camelia wrote: |
| Aahh, interesting... So what is it that puts off so many from using a physical sunscreen? Why do the large companies like L'Oreal use so many 'chemical' components in their sunscreens. What is the highest PPD of a physical sunscreen? Thanks for this information! |
Camelia, I heard from another forum member a SVR SPF 50 physical sunscreen offers a PPD of 20. It also has a tint to it too so u might wanna check it out  I haven't tried it myself yet as I heard it's a thick cream 
Here's the site to order samples from.
http://www.skincarecentral.biz/skincare-sun.html |
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Fri Jun 27, 2008 2:31 pm |
| Camelia wrote: |
| Aahh, interesting... So what is it that puts off so many from using a physical sunscreen? Why do the large companies like L'Oreal use so many 'chemical' components in their sunscreens. What is the highest PPD of a physical sunscreen? Thanks for this information! |
I think what puts many people off from physical sunscreen is that many (but not all!)of the physical sunscreens are so unpleasant. They can be thick, they can be gritty, they can be flakey, then can certainly leave a white cast. Trust me, I tried a lot of them! Luckily, I found a purely physical sunscreen that is guilty of none of those. I use the Devita sunscreen, and it really is an amazing product. It's 14% micronized zinc oxide and the texture is lovely and there's no white cast. Now that I found a mineral foundation to use over it (for the summer heat), I'm really satisfied.
I'm actually not that familiar with "ppd". However, I feel safe with zinc oxide as the sole sunscreen ingredient because zinc oxide offers broad spectrum protection. |
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Fri Jun 27, 2008 4:29 pm |
| Quote: |
| Aahh, interesting... So what is it that puts off so many from using a physical sunscreen? Why do the large companies like L'Oreal use so many 'chemical' components in their sunscreens. What is the highest PPD of a physical sunscreen? Thanks for this information! |
What puts off many is the much lower ppd value of a physical sunscreen and the texture/look of physical sunscreens. The ppd and texture are related, so if you find a physical sunblock that is not whitening/matte then it has lower ppd than one that is whitening. Physical sunblocks are made to sit on the surface of the skin and reflect the suns rays. So if you cant see the "whitening" of the product then it is not as efficient to reflect the UV rays. To make sunscreens less whitening, sunscreens use micronized zinc oxide/ti02 which effectively reduce the ability of the particles to reflect the most dangerous and aging UVA rays (however it does very well in the UVB range). Physical sunscreens can give a ppd of about 8 while chemical sunscreens like LRP and Bioderma can give a ppd as high as 35. So a big difference and thats why some prefer chemical over physical.
Physical sunscreens are equiv to the range of the best chemical sunscreens if they have min. conc. of 20% zinc oxide and are non-micronized. However, its not aestheically pleasing. There are benefits and downsides to both chemical and physical so its up to whatever you prefer.
Hope that helps! |
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Fri Jun 27, 2008 4:41 pm |
| Ocean14 wrote: |
| Quote: |
| Aahh, interesting... So what is it that puts off so many from using a physical sunscreen? Why do the large companies like L'Oreal use so many 'chemical' components in their sunscreens. What is the highest PPD of a physical sunscreen? Thanks for this information! |
What puts off many is the much lower ppd value of a physical sunscreen and the texture/look of physical sunscreens. The ppd and texture are related, so if you find a physical sunblock that is not whitening/matte then it has lower ppd than one that is whitening. Physical sunblocks are made to sit on the surface of the skin and reflect the suns rays. So if you cant see the "whitening" of the product then it is not as efficient to reflect the UV rays. To make sunscreens less whitening, sunscreens use micronized zinc oxide/ti02 which effectively reduce the ability of the particles to reflect the most dangerous and aging UVA rays (however it does very well in the UVB range). Physical sunscreens can give a ppd of about 8 while chemical sunscreens like LRP and Bioderma can give a ppd as high as 35. So a big difference and thats why some prefer chemical over physical.
Physical sunscreens are equiv to the range of the best chemical sunscreens if they have min. conc. of 20% zinc oxide and are non-micronized. However, its not aestheically pleasing. There are benefits and downsides to both chemical and physical so its up to whatever you prefer.
Hope that helps! |
I don't know much about ppd, but why do you say that zinc oxide has to be non micornized to be effective? I don't even know of a sunscreen that uses non micronized zinc oxide.
A 20% zinc oxide corresponds to about spf30, so a lower % will give a lower protection, but it will still be some protection. I don't think 20% zinc oxide is even necessary for everyday incidental exposure. |
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Fri Jun 27, 2008 5:09 pm |
| Quote: |
I don't know much about ppd, but why do you say that zinc oxide has to be non micornized to be effective? I don't even know of a sunscreen that uses non micronized zinc oxide.
A 20% zinc oxide corresponds to about spf30, so a lower % will give a lower protection, but it will still be some protection. I don't think 20% zinc oxide is even necessary for everyday incidental exposure. |
Hi Nimue, I was only saying 20% zinc oxide non-micronized would equal the amount of protection a chemical sunscreen like LRP and Bioderma can provide. You definitely don't need 20% zinc oxide for incidental exposure, I was just stating what it would take for a physical sunscreen to equal the protection of the best chemical sunscreens. Micronized zinc oxide is less effective in the UVA range then non-micronized, but is equivalent or better in the UVB range. Yes, most companies use micronized bc it gives a better look, however, it reduces the efficacy in the UVA range. Zinc oxide whether micronized or not, is STILL a great choice bc it can provide protection in the UVA range (doesnt cover all the uva rays) and UVB. For everyday use I think Devita or anyother product is a great choice.
About the SPF...it only indicates a sunscreens effectiveness in the UVB range (the burning rays). PPD is a value for the effectiveness in the UVA range (aging/cancer rays). So zinc oxide has very good spf values, but not as great ppd values. |
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Fri Jun 27, 2008 5:49 pm |
Ocean14,
I've never seen any evidence that micronized zinc oxide offers less protection against UVA compared to non micronized zinc oxide, so that's the point that I'm questioning. I would definitely like to see the sources for those statements. As it is, (based on my research into zinc oxide as a sunscreen) I'm just really skeptical that this is the case. I really did do a good amount of sunscreen research, which is why I'm so confident about my conclusions.
By the way, maybe you're confusing the terms "nano" and "micro"? Something that's "micro" sized is bigger than something that's "nano" sized by a factor of a 1000. I did see one study with the observation that nano sized zinc oxide gave slightly less protection than micro sized zinc oxide, and therefore a higher concentration of nano sized zinc oxide was required to match the protection of the micro sized zinc oxide.
| Ocean14 wrote: |
Hi Nimue, I was only saying 20% zinc oxide non-micronized would equal the amount of protection a chemical sunscreen like LRP and Bioderma can provide. You definitely don't need 20% zinc oxide for incidental exposure, I was just stating what it would take for a physical sunscreen to equal the protection of the best chemical sunscreens. Micronized zinc oxide is less effective in the UVA range then non-micronized, but is equivalent or better in the UVB range. Yes, most companies use micronized bc it gives a better look, however, it reduces the efficacy in the UVA range. Zinc oxide whether micronized or not, is STILL a great choice bc it can provide protection in the UVA range (doesnt cover all the uva rays) and UVB. For everyday use I think Devita or anyother product is a great choice.
About the SPF...it only indicates a sunscreens effectiveness in the UVB range (the burning rays). PPD is a value for the effectiveness in the UVA range (aging/cancer rays). So zinc oxide has very good spf values, but not as great ppd values. |
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Fri Jun 27, 2008 7:02 pm |
| Camelia wrote: |
Hi
I wonder if anyone here can explain why this is happening to me. I apply the Anthelios Pediatrics spf 50 sunblock everyday. It's alright, a bit shiny, a little too metalic and reflective but I suffer for the great PPD protection it gives my combination face.
I apply foundation very lightly and then powder. I have to powder because of the natural oils in my t-zone and the grease from the sunblock. When I'm done, I often assess that some areas look a little too powdery, especially above the lip and that little area a cm below the iris. So I set about trying to make it look moist there. A touch of Anthelios won't cut it - the metallic, reflective problem, you see. Then I discoved a little sample I had from Avene, spf50. Brilliant, great texture, better than Anthelios for me to be honest. So I put a little on the top of my lip and under the eye area. It's been quite hot here in the UK and what's happened??? My face feels burnt above my lip area. Grrrr. Why oh why has this happened?
Is Avene simply not as effective or longlasting as Anthelios or do they cancel each other out in some way?
If I trusted Avene protection more I would use the tinted spf 50 and forgo the Anthelios completely as I much prefer the texture and the peachy tint is very flattering and allows less foundation. I don't think the PPD is as high as Anthelios and now this has happened I do doubt its effectiveness. I also notice that the Avene recommends re-application every 2 hours!!! What planet are they living on for a busy woman to be able to do that all the time???
Anyone else compared the two brands? I'd love to know. |
It is possible the ethyhexyl methoxycinnamate (octinoxate) in the Avene sunblock is destabilizing the avobenzone in the LRP sunblock. The octinoxate plus avobenzone combination is known to be unstable. Even though the LRP sunblock contains other stabilizers of avobenzone, but maybe the octinoxate has tipped the balance in the stability of avobenzone.
I am surprised that Avene advocates reapplication every 2 hours. Ciba (manufacturer of Tinosorb M and S) actually market those sunscreen blockers as suitable for once-daily application. There are studies that indicate that Tinosorb M and S are photostable for at least 10 hours. |
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Fri Jun 27, 2008 7:14 pm |
| Quote: |
Ocean14,
I've never seen any evidence that micronized zinc oxide offers less protection against UVA compared to non micronized zinc oxide, so that's the point that I'm questioning. I would definitely like to see the sources for those statements. As it is, (based on my research into zinc oxide as a sunscreen) I'm just really skeptical that this is the case. I really did do a good amount of sunscreen research, which is why I'm so confident about my conclusions.
By the way, maybe you're confusing the terms "nano" and "micro"? Something that's "micro" sized is bigger than something that's "nano" sized by a factor of a 1000. I did see one study with the observation that nano sized zinc oxide gave slightly less protection than micro sized zinc oxide, and therefore a higher concentration of nano sized zinc oxide was required to match the protection of the micro sized zinc oxide. |
Hi Nimue, you are keeping me on my toes! I will quickly respond with some information that is readily available on the internet regarding my assertions. I am currently busy studying for the MCAT but when I have time I will get more of my sources, so I apologize in advance.
What I've continually stated is the inverse relationship of particle filters with UVA/UVB performance. I know the difference between "nano" and "micro" and will state again that zinc oxide at lower particle size (micro or nano) will have greater spf values, but lower ppd values. Micro is a particle size of 100-35nm, nano is 35-0nm and normal is 100-250nm.
From: Discovering an Optimum Small Micropigment
for High UV Shielding and Low Skin Whitening
Yun Shao, Ph.D., and David Schlossman - Kobo Products, Inc.
"The size reduction of titanium dioxide and zinc oxide can remarkably improve the appearance of a sunscreen lotion and improve SPF
score in most cases. However, when the size of titanium becomes too small, the absorption can shift to UVC and attenuation at UVA and UVB weakens. Butthe smaller TiO2 may show better synergetic effect with organic sunscreens. ZnO can be effective for SPF at the cost of UVA protection when its particle size is brought to under 130 nm."
"Due to the fact that the absorption peak of these ZnO dispersions has shifted to 360 nm and some UVA protection will be lost, a
larger size ZnO was added in order to improve PFA (UVA) score."
- there are graphs and clinical data that support these assertions. Just google the title to this article and can find it.
From: ZINC OXIDE POWDER BLENDS, THEIR PRODUCTION AND USE (a resource for formulators of sunscreens and cosmetics)
"Titanium dioxide is described as providing excellent protection against UVB along with effective UVA protection at a larger size where scattering may contribute significantly. However, such larger sizes may sacrifice some degree of SPF and transparency.
The protection afforded by zinc oxide is considered by Shao et al. 1999 to vary inversely with particle size. Also, zinc oxide is described as providing efficient UVA protection, often with a low SPF. One difficulty these findings present to the worker seeking to provide a broadspectrum
inorganic UV-protective agent suitable for topical application, is that desired sizes of
titanium dioxide particles may cause whitening on the skin, as may be understood from Fig. 5
of Shao 1999. (Nor does Shao et al. 1999 describe an adequate zinc oxide formulation."
Hope this helps with some of your questions. |
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Fri Jun 27, 2008 7:25 pm |
| Quote: |
It is possible the ethyhexyl methoxycinnamate (octinoxate) in the Avene sunblock is destabilizing the avobenzone in the LRP sunblock. The octinoxate plus avobenzone combination is known to be unstable. Even though the LRP sunblock contains other stabilizers of avobenzone, but maybe the octinoxate has tipped the balance in the stability of avobenzone.
I am surprised that Avene advocates reapplication every 2 hours. Ciba (manufacturer of Tinosorb M and S) actually market those sunscreen blockers as suitable for once-daily application. There are studies that indicate that Tinosorb M and S are photostable for at least 10 hours. |
Agree 100% m1rox! Its true that octinoxate in the presence of avobenzene even if stabilized causes it to become unstable.
Also tinosorb M and S are photostable much longer than 2 hours as m1rox states. Tinosorb M acts just like a physical agent that stays on the skin surface and reflects incoming UV rays, hence it is VERY photostable. |
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Fri Jun 27, 2008 8:06 pm |
Ocean14,
I looked up the study that you're referring to:
http://www.koboproductsinc.com/Downloads/IFSCC2004.pdf
This is actually the same study that I just mentioned that had the observation that nano sized zinc oxide gives less protection, so I'm really glad I was able to look at it again, since I had forgotten where I had seen it in the first place!
First of all, I want to point out that this study was performed by someone selling a product... This is not something that's on pubmed. For now, I'll assume that these people are trustworthy, but it's not a given.
Your ranges for nano, micro, and normal sizes are not what I had in mind. I figure that the accepted (purely mathematical) border between something that's nano and micro sized is 100 nm, which is also .1 of a micro. Micro is anywhere from .1 micro (= 100 nm) and 100 micro (=100,000 nm, =.0001). I would say that "normal sized" in this context would have to be something bigger than 100 micro.
If the industry decided to label 35 nm as the border between nano and micro, I guess I'm surprised and it doesn't make much sense to me. It seems like an arbitrary border and it doesn't make mathematical sense.
Anyway back to the study: the particle sizes used are all sizes that I would label "nano" and they range from comparatively larger to comparatively smaller nano sizes, but they're all nano sized to me.
| Ocean14 wrote: |
| Quote: |
Ocean14,
I've never seen any evidence that micronized zinc oxide offers less protection against UVA compared to non micronized zinc oxide, so that's the point that I'm questioning. I would definitely like to see the sources for those statements. As it is, (based on my research into zinc oxide as a sunscreen) I'm just really skeptical that this is the case. I really did do a good amount of sunscreen research, which is why I'm so confident about my conclusions.
By the way, maybe you're confusing the terms "nano" and "micro"? Something that's "micro" sized is bigger than something that's "nano" sized by a factor of a 1000. I did see one study with the observation that nano sized zinc oxide gave slightly less protection than micro sized zinc oxide, and therefore a higher concentration of nano sized zinc oxide was required to match the protection of the micro sized zinc oxide. |
Hi Nimue, you are keeping me on my toes! I will quickly respond with some information that is readily available on the internet regarding my assertions. I am currently busy studying for the MCAT but when I have time I will get more of my sources, so I apologize in advance.
What I've continually stated is the inverse relationship of particle filters with UVA/UVB performance. I know the difference between "nano" and "micro" and will state again that zinc oxide at lower particle size (micro or nano) will have greater spf values, but lower ppd values. Micro is a particle size of 100-35nm, nano is 35-0nm and normal is 100-250nm.
From: Discovering an Optimum Small Micropigment
for High UV Shielding and Low Skin Whitening
Yun Shao, Ph.D., and David Schlossman - Kobo Products, Inc.
"The size reduction of titanium dioxide and zinc oxide can remarkably improve the appearance of a sunscreen lotion and improve SPF
score in most cases. However, when the size of titanium becomes too small, the absorption can shift to UVC and attenuation at UVA and UVB weakens. Butthe smaller TiO2 may show better synergetic effect with organic sunscreens. ZnO can be effective for SPF at the cost of UVA protection when its particle size is brought to under 130 nm."
"Due to the fact that the absorption peak of these ZnO dispersions has shifted to 360 nm and some UVA protection will be lost, a
larger size ZnO was added in order to improve PFA (UVA) score."
- there are graphs and clinical data that support these assertions. Just google the title to this article and can find it.
From: ZINC OXIDE POWDER BLENDS, THEIR PRODUCTION AND USE (a resource for formulators of sunscreens and cosmetics)
"Titanium dioxide is described as providing excellent protection against UVB along with effective UVA protection at a larger size where scattering may contribute significantly. However, such larger sizes may sacrifice some degree of SPF and transparency.
The protection afforded by zinc oxide is considered by Shao et al. 1999 to vary inversely with particle size. Also, zinc oxide is described as providing efficient UVA protection, often with a low SPF. One difficulty these findings present to the worker seeking to provide a broadspectrum
inorganic UV-protective agent suitable for topical application, is that desired sizes of
titanium dioxide particles may cause whitening on the skin, as may be understood from Fig. 5
of Shao 1999. (Nor does Shao et al. 1999 describe an adequate zinc oxide formulation."
Hope this helps with some of your questions. |
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Sat Jun 28, 2008 1:11 am |
Nimue,
I am by no means a skin care expert, I am just trying to be a helpful member on the board. Please stop insinuating that I don’t know what “micro” or “nano” mean. I am a biology major at a very accomplished university. For someone who says quote “I am not that familiar with ppd,” I don’t understand why you state “I really did do a good amount of sunscreen research, which is why I'm so confident about my conclusions” regarding zinc oxide when its known zinc oxide does not provide ppd values of other sunscreens. If you dont know much about ppd then, you wouldnt be confident knowing particle size and ppd value. Zinc oxide can get a ppd of roughly 8, which means it is not as effective in the UVA range as chemical sunscreens like bioderma and LRP. That’s all I am trying to say. Zinc oxide is not as effective in the UVA-I range because it cannot cover the full spectrum, however LRP and Bioderma can cover fully up to 400 nm. Micronized, or the smaller the particle size, the less effective in the UVA range, but more effective in the UVB range. PPD stands for persistent pigment darkening and is an indicator of the efficacy of a sunscreen in the UVA range. A great resource for you to look at is makeupalley in the sunscreen notepad (http://makeupalley.com/account/vn.asp?u=sunscreenFAQ and http://makeupalley.com/account/vn.asp?u=sunscreens) which will give you an indication about the effectiveness of different sunscreens and how they differ. They too state the higher ppd values of chemical sunscreens and how ppd of physicals relate to particle size. They provide full documentation of all the facts. Here are some more things I have found:
Physical sunscreens: On the comeback trail
Balaji D More
Clinical Pharmacologist and Manager, Medico-marketing and Clinical Research, Steifel Pharmaceuticals India Ltd., India
(this even has quotes from research on pubmed…see acknowledgements, and also quotes the study I posted in the previos post)
"The UVA coverage ability of microfine physical block particles depends primarily on the particle size."
"UVA attenuation is better than UVB attenuation with particles of larger size. [12] Micronized forms have the ability to attenuate both UVB and UVA II with a steep or gradual drop off in absorbance in the upper UVA I range"
"For ZnO and TiO 2 , particle size of ~0.1 micron is the most effective in attenuating UV radiation. [13] UV blocking capacity decreases as the particle size goes below 0.1 micron whereas above this size, whitening can occur.Very fine particles have a tendency to agglomerate to form large particles."
Another:
Epstein FH. The pathogenesis of melanoma induced by ultraviolet radiation. N Engl J Med. 1999;340:1341-1348Palm MD, O'Donoghue MN. Update on photoprotection. Dermatol Ther. 2007;20:360-376.
“Micronized forms of inorganic agents helped reduce the whitish residue; however, they also caused less scattering of light. Prior to micronization, inorganic agents were able to block long wavelengths such as UVA. After micronization, only shorter wavelengths such as UVB could be reflected.”
Another: (http://www.hautkrebswoche.ch/fileadmin/hautkrebswoche/melanoma.ch/Fachtexte/Studie__Lautenschlager_07.pdf)
Roelandts R. Shedding light on sunscreens. Clin Exp Dermatol
1998; 23: 147–57.
"Micronisation shifts the protective spectrum, via its property as an absorbing agent, towards shorter wavelengths.69
Decreasing particle size to 10–50 nm(micronised form) results in less scattering of visible light,leading to a more cosmetically acceptable product.
"Microfine titanium
dioxide has an absorption profile greater in UVB than does microfine zinc oxide; by contrast, zinc oxide was found to be more effective in UVA protection (up to 380 nm) than was microfine titanium dioxide.74 These
effects vary largely due to the particle size of the substances. Microparticles tend to agglomerate and aggregate due to electrostatic effects, resulting in potentially greater loss in efficacy.
Another:
PALMER, Bruce, R. KAUFFMAN, James, W. STAMATAKIS, Penelope: Attenuation of POLYMER SUBSTRATE DEGRADATION DUE TO ULTRAVIOLET RADIATION
"Referring now to FIGURE 5, the transmittance for a wurtzite zinc oxide particle containing layer with an fh of 0.05 micrometer corresponding to a loading of 280 mg/m2 is illustrated as a function of particle diameter and wavelength. The transmittance of ultraviolet radiation by a polymer substrate layer containing zinc oxide particles is different from a polymer substrate layer containing titanium dioxide particles. As illustrated by FIGURE 5, small zinc oxide particles provide the highest attenuation, and the effectiveness of the particles declines rapidly as size increases. Since the real portion of the refractive index of wurtzite zinc oxide is smaller than that for rutile titanium dioxide, absorption plays a more important role for zinc oxide in attenuation of ultraviolet radiation than does scattering."
Another:
FDAs Proposed Ruling on Sunscreen Protection Products
Neha U. Sheth, PharmD
University of Maryland, School of Pharmacy
Baltimore, Maryland
"Protection at various wavelengths depends upon the size of the particle of active material. Therefore, one should prevent and control agglomeration of these particles, otherwise the agglomerates will have optical behavior of large particles. In other words, in the cases of inorganic filters, this represent less protection against UV rays and, consequently, a decrease in the sunshine protection factor (SPF), besides causing a whitish effect on the skin."
Also, the FDA has no real definition of micronized and nano size particles and products and are not required to state it on the label. Therefore, products are stated to have micronized forms of say 50nm exactly like what is reported in an excerpt I cited above. So that is why I put up those ranges in my previous post of nm sizes bc that is what I have seen, it is not a standardized size of micronized, nano and normal bc there ISNT ANY! From the cosmeticdatabase: "Until FDA requires appropriate labeling it will remain difficult for consumers to clearly distinguish which ones contain nano-size particles if they care to avoid them. In the interim the easiest way for a consumer to judge the particle size of the zinc or titanium in their sunscreen is by the tint that it leaves on skin when applied. A good rule of thumb: If your zinc or titanium sunscreen goes on clear it is nanosized.According to the cosmeticdatabase.com micronized sunscreens do contain nano particles
So, it could be listed as zinc oxide and we don't know if it's "regular," "micronized," or "nano." I stated the above values as ranges in nm's of particle sizes that I found to be effective. 35nm or less is the particle size not allowed in Europe bc they classify it as "nano" particles which are banned there so I stated it as nano. Sorry for the confusion.
In response to your quote, "First of all, I want to point out that this study was performed by someone selling a product... This is not something that's on pubmed. For now, I'll assume that these people are trustworthy, but it's not a given." Pubmed does not have every clinical trial/research ever done, in addition it too has significant no. of articles regarding scientists who sell products: ie) Daniel Yarosh. The company that performed the test are not selling a specific sunscreen or product, they provide raw materials to manufacturers and do research on the most effective way to formulate products.
You don't have to believe me, I am just simply telling you what I have learned. I think physical sunscreens are great too, I just dont believe they cover the same range as some of the best chemical formulations. |
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Sat Jun 28, 2008 1:44 am |
| I hope my last post didn't come across as being mean!!! I re-read it and did not like the tone of my voice. I think sitting in the library and studying all day is doing it to me. I need sleep! |
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Sat Jun 28, 2008 6:30 am |
Ocean14,
I also don't want to be mean. I am in fact saying that you're a little confused with micros and nanos. It's ok! Sometimes it's confusing to me too! I'm definitely not trying to insult you about it.
The border between micro and nano is in fact 100 nm. When you say that the border is 35 nm, you're just making things up. (No matter what they say in Europe  They probably picked 35 nm because they decided that's too small for them)
Micro=1*10^-6 =.000001
Nano= 1*10^-9 =.000000001
Micro is bigger than nano by a factor of 1000. 100 nm is bigger than 35 nm by a factor of about 3. The fact is, the particle sizes in the articles you quoted are in the nano range. When you say that micro sized zinc oxide are not effective against UVA, this is wrong and very harmful information, which is why I can't just let it go. |
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Sat Jun 28, 2008 6:37 am |
| One thing that's confusing to most people is that "micronized" is the term generally used to refer to a process that makes particles really small. When "micronization" results in a nano sized particle, that's really misleading! I think it's just a bad term for it, and there should have been a different term for making stuff small, since now we can make it much smaller than in the micro range. I can totally understand how confusing that is! |
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Sat Jun 28, 2008 6:51 am |
Ocean14,
Also, maybe you're not confused about micro and nanos, but then in that case, you're talking about them in misleading ways to make me think that you're confused. It's probably just the lack of sleep!
I have the most issue with this statement from you:
"Micro is a particle size of 100-35nm, nano is 35-0nm and normal is 100-250nm." |
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