35 replies to this topic

[miklu]

Hi,

I have been doing some research on sunscreen filters, and it seems that zinc oxide (ZnO) is the only single filter offering broad-spectrum protection (in UVB, UVAI and UVAII regions). Adding this to the fact that zinc oxide is photostable makes me wonder: what are the reasons that people and manufacturers still bother with other filters? I can think of three:

1) white cast (a subjective problem);
2) zinc oxide (like other physical blockers) isn't rubbing-resistant (fixable with proper usage);
3) the possibility that the protection offered by ZnO is disproportionately weighted towards the UVB and UVAII regions, and not so much towards the photoaging-inducing UVAI region.

Problem 3 is arguably the most serious (as it's non-subjective and not fixable with proper usage), but I haven't seen any literature supporting it.

[mustardseed41]

http://sun1.awardspa.../sunscreens.htm

http://makeupalley.c...eenFAQ#physical

[niner]

People use other sunscreens because they don't like to go out looking like a mime.

[okok]

People use other sunscreens because they don't like to go out looking like a mime.

haha, exactly. but you can try adding some skin-tone mineral powder. (and look like you're wearing make-up).

[Ben]

People use other sunscreens because they don't like to go out looking like a mime.

haha, exactly. but you can try adding some skin-tone mineral powder. (and look like you're wearing make-up).

which is just what every guy wants.

[miklu]

http://sun1.awardspa.../sunscreens.htm

http://makeupalley.c...eenFAQ#physical

Thanks for the excellent links. OK, so ZnO alone can't achieve very high SPF and/or PPD.

[Eva Victoria]

Hi,

I have been doing some research on sunscreen filters, and it seems that zinc oxide (ZnO) is the only single filter offering broad-spectrum protection (in UVB, UVAI and UVAII regions). Adding this to the fact that zinc oxide is photostable makes me wonder: what are the reasons that people and manufacturers still bother with other filters? I can think of three:

1) white cast (a subjective problem);
2) zinc oxide (like other physical blockers) isn't rubbing-resistant (fixable with proper usage);
3) the possibility that the protection offered by ZnO is disproportionately weighted towards the UVB and UVAII regions, and not so much towards the photoaging-inducing UVAI region.

Problem 3 is arguably the most serious (as it's non-subjective and not fixable with proper usage), but I haven't seen any literature supporting it.

There is Tinosorb M that provides very high UVAI UVA II and UVB protection/%. It is only approved in the EU, AU and JP. It is also whitening on the skin. It has a higher UVA protection efficiency compared to ZnO. It is also highly photostable (like ZnO).

ZnO (natural and micronized) is an excellent UVA II and UVA I (!) filter. It is a weaker UVB filter though when the micronized form is used. It is best to be combined with either TiO2 or organic UVB filter. It has shown synergistic effect with OMC and boosting effect on OMC's UVB protection.
Nano ZnO is on the other hand an excellent UVB filter and an ok-ish UVA II filter, but has no coverage in UVA I.

Manufacturers use other types of UV filters because of the whitening effect of ZnO. And the costs. ZnO is a very expensive UV filter. Organic UV filters are much cheaper and need less actives to achieve high SPF. TiO2 is a good alternative because it gives high SPF/% esp. the micro and nano variants. Today there are manufacturers of TiO2 that manage to produce TiO2 that has high SPF/% and 1/3 UVA protection as recommended by the EU. In reality, of course UVA protection is barely up to 360 nm.

I personally prefer ZnO as UVA filter. In my products I use it with OMC and ZnO up to 20% concentration. It gives a bit of a white cast to the skin but because of ZnO's refractive index is lower than that of TiO2 it is still very acceptable. I have also experimented with adding some iron oxide so it got a more natural tint.

There are loads of ZnO out there with different coatings that increase its UVB and UVA protection abilities.
The most effective enhancement (for higher UVB protection) that also makes it even more cosmetically elegant is the version coated with Triethoxycaprylylsilane.

[mustardseed41]

What about the above link saying that zinc oxide sunscreens have a low PPD level?

[happy lemon]

Hi Eva,

Need your help.

I have been using Neutrogena's Ultra Sheer (Helioplex) for 6 months and just learnt that once UV energy can cause sunscreen breakdown & then chemical sunscreens can get into the skin; therefore I am looking for a physical one.

May you take a look at the ingredients of Neutrogena and see if it is so easily broken down by UV (because I still have 3 tubes unopened).

Water, Homosalate, Butyloctyl Salicylate, Benzophenone-3, Ethylhexyl Salicylate, Cetyl Dimethicone, Octocrylene, C12-15 Alkyl Benzoate, Silica, Butyl Methoxydibenzoylmethane, Styrene/Acrytates Copolymer, Glyceryl Stearate, PEG-100 Stearate, Polyamide-5, Cetyl Alcohol, VP/Hexadecene Copolymer, Potassium Cetyl Phosphate, Cyclopentasiloxane, Diethylhexyl 2, 6-Naphthalate, Ethylhexylglycerin, Dimethicone/Vinyl Dimethicone Crosspolymer, Benzyl Alcohol, Methylparaben, Ethylparaben, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Bisabolol, Propylparaben, Disodium EDTA, Butylene Glycol, Fragrance, Portulaca Oleracea Extract, Acrylates/Dimethicone Copolymer, Tocophery Acetate, Ascorbic Acid, Pantothenic Acid, Retinyl Palmitate

From the EDS forum, people are talking about physical sunscreen and some of them suggest an Australian brand "Invisible Zinc".

The Environmental Skin Protector contains 20% Zinc Oxide, micronized, not nano and it is light, non greasy & matte finish; that it is why I am interested in it.

Do you think it is a good UVA & UVB sunscreen?

http://www.ganehill....oduct/range.htm
http://www.ganehill....au/not_nano.htm

The ingredients are as follows:

Aqua, Zinc Oxide, C12-15 Alkyl Benzoate, Isostearyl Neopentanoate, Cyclopentasiloxane, Glycerin, Methyl Glucose Sesquistearate, Cetearyl Alcohol, Cetearyl Glucoside, PEG-20 Methyl Glucose Sesquistearate, Xanthan Gum, Diazolidinyl Urea, Benzyl Alcohol, Butylene Glycol, Citrus Medico Limonum (Lemon) Fruit Extract, Fumaria Officinalis Extract, Fumaric Acid, Disodium EDTA, Tocopheryl Acetate

[niner]

I have been using Neutrogena's Ultra Sheer (Helioplex) for 6 months and just learnt that once UV energy can cause sunscreen breakdown & then chemical sunscreens can get into the skin; therefore I am looking for a physical one.

The point of the Helioplex formulation is that it's photostable, as I understand it.

[Eva Victoria]

Hi Eva,

Need your help.

I have been using Neutrogena's Ultra Sheer (Helioplex) for 6 months and just learnt that once UV energy can cause sunscreen breakdown & then chemical sunscreens can get into the skin; therefore I am looking for a physical one.

May you take a look at the ingredients of Neutrogena and see if it is so easily broken down by UV (because I still have 3 tubes unopened).

Water, Homosalate, Butyloctyl Salicylate, Benzophenone-3, Ethylhexyl Salicylate, Cetyl Dimethicone, Octocrylene, C12-15 Alkyl Benzoate, Silica, Butyl Methoxydibenzoylmethane, Styrene/Acrytates Copolymer, Glyceryl Stearate, PEG-100 Stearate, Polyamide-5, Cetyl Alcohol, VP/Hexadecene Copolymer, Potassium Cetyl Phosphate, Cyclopentasiloxane, Diethylhexyl 2, 6-Naphthalate, Ethylhexylglycerin, Dimethicone/Vinyl Dimethicone Crosspolymer, Benzyl Alcohol, Methylparaben, Ethylparaben, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Bisabolol, Propylparaben, Disodium EDTA, Butylene Glycol, Fragrance, Portulaca Oleracea Extract, Acrylates/Dimethicone Copolymer, Tocophery Acetate, Ascorbic Acid, Pantothenic Acid, Retinyl Palmitate

From the EDS forum, people are talking about physical sunscreen and some of them suggest an Australian brand "Invisible Zinc".

The Environmental Skin Protector contains 20% Zinc Oxide, micronized, not nano and it is light, non greasy & matte finish; that it is why I am interested in it.

Do you think it is a good UVA & UVB sunscreen?

http://www.ganehill....oduct/range.htm
http://www.ganehill....au/not_nano.htm

The ingredients are as follows:

Aqua, Zinc Oxide, C12-15 Alkyl Benzoate, Isostearyl Neopentanoate, Cyclopentasiloxane, Glycerin, Methyl Glucose Sesquistearate, Cetearyl Alcohol, Cetearyl Glucoside, PEG-20 Methyl Glucose Sesquistearate, Xanthan Gum, Diazolidinyl Urea, Benzyl Alcohol, Butylene Glycol, Citrus Medico Limonum (Lemon) Fruit Extract, Fumaria Officinalis Extract, Fumaric Acid, Disodium EDTA, Tocopheryl Acetate

Hi Happy Lemon,

First Neutrogena's sunscreen may indeed be broken down by UVA. The only chemical sunscreen somewhat stabilizing ingredient I have found is Dimethicone/Vinyl Dimethicone Crosspolymer (if it is an elastomer blend). But it is impossible to know whether it is a powder or an elastomer blend.

Products containing "Invisible Zinc" contain nano ZnO. Very low PPD and no UVA I protection at all.
My mistace about the brand Invisible Zink. Just found this:
TOP SUNSCREEN BRANDS PLEDGE TO AVOID USING HIGH RISK NANO INGREDIENTS — Friends of the Earth Australia
http://www.foe.org.a...no-ingredients/

If it is true that they no longer use nano particles then it might be a good choice too. It seems they use 13-18% ZnO in their products.

"Megan Gale Invisible Zinc Sunscreen 16% Zinc Oxide
Active Ingredient: Zinc Oxide 154 mg/g.
Other Ingredients: Water, Zinc Oxide, Propylene glycol, polyethylene, sodium chloride, Caprylic/capric triglyceride, Diazolidinylurea, Glyceryl Laurate, Iodopropynyl butylcarbanate, Isostearyl neopentanoate, PEG-30 Dipolyhydroxystearate" from http://www.essentialdayspa.com/forum/viewthread.php?tid=21741

the only question remains: since it is a water based sunscreen and ZnO is oil soluble, do they use water dispersed ZnO? I don't see any coating of the ZnO either. I'm still not impressed.

Your last sunscreen seem to be good with 20% ZnO (micro). But I don't like Citrus Medico Limonum (Lemon) Fruit Extract though.

Edited for correction about Invisible Zinc.

Edited by Eva Victoria, 16 January 2010 - 05:21 PM.

[Eva Victoria]

What about the above link saying that zinc oxide sunscreens have a low PPD level?

PPD level is measured at 360-370nm. ZnO even at high concentration won't give as high PPD values (at this nm) as AVO will (AVO peaks at 357nm). However, ZnO has an excellent and considerably high value at 383nm (where only Tinosorb M can match its values. znO peaks at 380-383 nm; Tinosorb M at 388nm).
So all in all, ZnO gives a broader and 100% photo stable UVA II and UVA I protection as long as the particle size is about 60-200nm (or higher). (E.g. no nano particles).
It is also very important to note the percentage it is used. Surface coating is a very important aspect and what media it is dispersed in. How it is dispersed and if organic filter(s) used how they are stabilized. Even though ZnO stabilizes OMC.

A thought on AVO. It is a very commonly used UV filter all over the world. It is approved everywhere and it is very well marketed and well known among the general public.
However it is extremely photo unstable. OCR stabilizes it somewhat but not nearly as good as it should be.
There are some very new approaches to make it fully photostable. There is a new photostabilizing agent for AVO. It is called SolaStay (INCI:Ethylhexyl methoxycrylene) and got approved a few days ago in the EU. So if you see this name in the INCI listing along with AVO then you can be sure that the sunscreen is photostable.
Tinosorb S is a good photo stabilizer for AVO. It is only approved in the EU, JP, AU.

The other question about AVO is that it is only approved up to 3% concentration in the US. Is that enough for sensible UVA protection? (It is allowed in 5% concentration in AU and in the EU, and up to 10% in JP).


There are other good photostable chemical UVA absorbers like Uvinul A Plus, but it is only approved in the EU and JP. (it peaks at 353 nm).

[happy lemon]

The point of the Helioplex formulation is that it's photostable, as I understand it.

Niner, Yes, I am aware of it from the advertising of Neutrogena but I would like to verify it with someone who has profund knolwedge of sunscreen, like Eva; I am a bit skeptical with advertisement.

First Neutrogena's sunscreen may indeed be broken down by UVA......Your last sunscreen seem to be good with 20% ZnO (micro). But I don't like Citrus Medico Limonum (Lemon) Fruit Extract though.

Eva, thank you so much for educating me on sunscreen. I have just started to use sunscreen for 6 months; in the past, I did not use any even I went swimming or trekking or did outdoor sports. Now I pay for it as I see very deep NL fold and sagging on my cheeks.

The Environmental Skin Protector, that I am interested in, contains 20% Zinc Oxide is one sunscreen under the Australian brand Invisible Zinc.

I have tried sample made of Tinosorb M, Mexoryl XL, Mexoryl SX but found them bit greasy; as I live in Asia and do sweat a lot; therefore, I prefer using a sunscreen which is light & matte finish as what the Environmental Skin Protector claims.

Thanx again!

[niner]

First Neutrogena's sunscreen may indeed be broken down by UVA.

Eva Victoria, do you have any data on the stability of the Helioplex formulation? It must be better than nothing as an Avobenzone stabilizer, although I hesitate to rely on the Neutrogena/J&J claims alone. I've seen third party testing data for the UVA blocking ability of a variety of US-available sunscreens, and the best of the Neutrogena Helioplex sunscreens are pretty good for the price. I would like to be able to apply a sunscreen once in the morning, then go about my normal activities, which would involve a few minutes of sun exposure here and there, going from house to car and car to other buildings, but spending the bulk of my time indoors. Reapplication every 2 hours is out of the question, but given the small amount of total irradiance that I'm getting, it doesn't seem like I should have to. Is my logic OK here, or am I missing something? In other words, am I correct in thinking that the stability of a given filter depends on the total dose of UV photons that it receives, rather than the time that it has been on the skin?

[Eva Victoria]

First Neutrogena's sunscreen may indeed be broken down by UVA.

Eva Victoria, do you have any data on the stability of the Helioplex formulation? It must be better than nothing as an Avobenzone stabilizer, although I hesitate to rely on the Neutrogena/J&J claims alone. I've seen third party testing data for the UVA blocking ability of a variety of US-available sunscreens, and the best of the Neutrogena Helioplex sunscreens are pretty good for the price. I would like to be able to apply a sunscreen once in the morning, then go about my normal activities, which would involve a few minutes of sun exposure here and there, going from house to car and car to other buildings, but spending the bulk of my time indoors. Reapplication every 2 hours is out of the question, but given the small amount of total irradiance that I'm getting, it doesn't seem like I should have to. Is my logic OK here, or am I missing something? In other words, am I correct in thinking that the stability of a given filter depends on the total dose of UV photons that it receives, rather than the time that it has been on the skin?

It is a bit more complicated than that.
the amount of UV radiation is crucial when it comes to chemical sunscreens. But they tend to sink in the skin after a certain amount of time which (some scientist believe) can damage (by oxidation in the presence of UVR) your skin.
Hence reapplication of chemical filters every 2 h is crucial.

If you don't want to reapply your sunscreen so often esp. during a normal day. I would recommend to use a physical sunscreen. At SPF 15 it would be sufficient protection for your activities and it would not be visible on your skin either.

I'll look into some studies about Helioplex and post it here later.

One more thought: there is actually a TiO2 that does protect up to 385nm. It is engineered at the University of Oxford (UK) and it is called Optisol. It can also be a very good alternative for ZnO.
This is from the studies for Optisol:

"This novel inorganic sunscreen incorporates manganese ions into the structural
lattice of titanium dioxide thereby imparting key functional benefits unparalleled by any standard or coated material commercially available.
Manganese in the bulk – minimizes free radical generation.
Manganese at the surface – provides free radical scavenging."

[mustardseed41]

We have been down this road before about the need to apply sunscreens every 2 hours. Unless one is out in direct sunlight, swimming, at the beach, working, etc. there is no evidence for the need to re-apply every 2 hours. Good luck to woman who wear make-up trying that.

[happy lemon]

Eva,

I do have 2 more questions:

1. In the morning, I put DIY Vitamin C serum (L-Ascorbic Acid) on my skin before Neutrogena sunscreen. If I switch to physical one with Zinc Oxide; will the Zinc Oxide be oxidized by the acid?

2. I would like to add copper peptide serum in my am routine & aleternate with Vit C serum on every other day? Does copper peptide go well with Zinc Oxide sunscreen?

[Eva Victoria]

I do have 2 more questions:

1. In the morning, I put DIY Vitamin C serum (L-Ascorbic Acid) on my skin before Neutrogena sunscreen. If I switch to physical one with Zinc Oxide; will the Zinc Oxide be oxidized by the acid?

Not that I know of.

2. I would like to add copper peptide serum in my am routine & aleternate with Vit C serum on every other day? Does copper peptide go well with Zinc Oxide sunscreen?

As far as I know peptides do not interact with ZnO. In badly formulated sunscreens some type of TiO2 along with ZnO can make the formulation unstable. But that only means that the formulation itself can precipitate.It is not oxidized neither generates free-radicals.

[happy lemon]

Thx Eva; I m ready to use physical sunscreen!

Anyone of you has this bad habit like mine: once you don't like the product, you'd like to use it up asap; subconsciously & purposely you'll apply it more and more on your skin.

[rashlan]

Has anyone noticed that optisol sell their own sunscreen now? http://www.optisolsundefence.com

[eason]

Regardless of photostability, Helioplex isn't that great. It utilizes oxybenzone and other harsh ingredients.

[niner]

Regardless of photostability, Helioplex isn't that great. It utilizes oxybenzone and other harsh ingredients.

It has one major advantage over sunscreens that are effective in UVA and are also photostable; it's not expensive. I just looked at the Optisol product; 25 GBP (1GBP = 1.6USD) for a 100ml tube. Helioplex is, i dunno, a third of that? A quarter? I've been using it for a long time and haven't noticed any harshness problems.

[rollo]

Thx Eva; I m ready to use physical sunscreen!

Anyone of you has this bad habit like mine: once you don't like the product, you'd like to use it up asap; subconsciously & purposely you'll apply it more and more on your skin.

word

[okok]

cf the degradation issue, how does this apply to bottled sunscreen? better to always keep in a dark place?

[happy lemon]

By chance came across the following thread.

For those who are looking for zinc only sunblocks.

http://www.essential...d.php?tid=35450

Edited by happy lemon, 15 February 2010 - 03:14 PM.

[Eva Victoria]

Happy Lemon, I'd like to use your charts here. I know the first one is usually used by BASF for Z-Cote.

AVO do not protect fully in the UVAI. It peaks at 358nm and almost no protection after 390nm. ZnO do not provide adequate protection in the whole UV spectrum unlike these charts show.



If ZnO is non-micro/nano than the UVB protection is minimal. But UVAI is extremely good (up to 520nm).
Micro ZnO provides better UVB protection and less UVAI protection. Though the UVAI protection is still concidered good (385nm). this is the best broad spectrum protection in one singel filter. Should be combined with organic filters though like OMC or Polysilicone-15 (not permitted in the US) to achieve better UVB protection. (ZnO stabilizes OMC).

Nano-ZnO provides very good UVB protection, just as good as TiO2 but UVAII protection is partial and UVAI is as good as non-existent.

Why ZnO is such a good sunscreen agent alone is because it can really give broad-spectrum protection in one single agent when it is used in high enough concentration (15%+). AND it is inherently photo-stable.
While organic filters provide higher SPF (UVB protection) and UVAII protection pr. percent of active required to achieve the required SPF/PPD (and they are conciderably cheaper when it comes to costs) they tend to provide narrower protection scale and they tend to be extremely photo-unstable. Hence they should be reapplied every 2 hours and combined with each other to provide broader protection.
The only true organic UVAI protection is possible with Tinosorb M. But it is not really an organic filter either. It is a so called organic particle filter. It is also inherently photostable. Its real advantage is that it is water soluble while almost all other filters (inorganic filters included) are oil soluble. The other good thing is that it is very affordable and it gives high UVA II and I protection pr. % active used. The drawback: it is not worldwide approved.

Why organic filters are so popular is because they are cheap to produce. Much less actives are needed to achieve high SPF sunscreens or UVA(II) protection. The profit can be increased much more than using 20% ZnO to achieve a sunscreen with lower SPF (but with the same UVA(II) protection or lower). The cost for this sunscreen is about 7-10 times more than achieving the same UVA(II) protection with organic filters (like AVO).
Organic filters are much more cosmetically elegant as well. So it is easier to sell.
But from the consumers' point they are though elegant (or more elegant) and cheaper, they are photo-unstable and have to be reapplied every 2h.

With todays technology it is possible to produce ZnO containing sunscreens with 15-25% ZnO, combined with OMC (7.5%) to achieve high SPF (50) and adequate UVA protection (PPD20). These sunscreens can be formulated mattish (while organic ones are almost always very oily and shiny). ZnO containing sunscreens with the right formulation can be used as visual skin perfectors (while organics actually make the imperfections of the skin look more pronounced).
The Refractive Index of ZnO can easily be turned into a very nice skin-veil that actually hides imperfections and makes it more dewy.

But the real difference between an organic sunscreen and a ZnO (15%+) containing one is that the UVAI protection from 385nm is usually non-existent for organic sunscreens (even when they contain TiO2*) while the one with 15%+ ZnO has at least PPD 10 at 385nm and about 4-8 at 400nm (depending on the particle size). So it provides lower SPF and PPD (UVAII) but it actually does cover the whole UVA spectrum! And again it is inherently photostable!

(PPD 20 means 95% protection; 15 means 93% protection; 8 means 87% protection!)

So what is better a sunscreen with AVO with an impressive PPD 30 (96% protection**) at 360nm but about 2 (50% protection**) at 390nm and 0 at 400nm, OR a ZnO containing sunscreen with a modest PPD 15 (93% protection at 360nm and PPD 17 -94% protection- at 385nm) and about PPD 8 (87% protection) at 400nm?

*Inorganic filters cannot be combined with AVO in the US! Inorganic filters are: TiO2, TinOxide, ZnO.
** Sunscreens containing AVO usually loose their protecting abilities by 50% after as little as 20 min after application.

Reduced: 68% of original size [ 759 x 539 ] - Click to view full image

http://www.imminst.o...o...0&start=100

Attached Files

•  UV_Spectrum_diff._UV_filters.pdf   122.16KB   92 downloads

[HallStar Co.]

What about the above link saying that zinc oxide sunscreens have a low PPD level?

A thought on AVO. It is a very commonly used UV filter all over the world. It is approved everywhere and it is very well marketed and well known among the general public.
However it is extremely photo unstable. OCR stabilizes it somewhat but not nearly as good as it should be.
There are some very new approaches to make it fully photostable. There is a new photostabilizing agent for AVO. It is called SolaStay (INCI:Ethylhexyl methoxycrylene) and got approved a few days ago in the EU. So if you see this name in the INCI listing along with AVO then you can be sure that the sunscreen is photostable.

Hi- This certainly sounds like an educated group on sunscreen ingredients! I just wanted to follow-up on Eva's comments regarding SolaStay S1 but do not want to derail the thread with needless promotion. If you're interested in learning more about this new photostabilizer, please visit us at http://www.hallstar.com/solastay

Thanks for your time!

[chiaberry]

Hi- This certainly sounds like an educated group on sunscreen ingredients! I just wanted to follow-up on Eva's comments regarding SolaStay S1 but do not want to derail the thread with needless promotion. If you're interested in learning more about this new photostabilizer, please visit us at http://www.hallstar.com/solastay

Thanks for your time!

Hi please could you keep us updated on which commercial products are using your product? We would be most interested to try.

Many thanks.

[mustardseed41]

First Neutrogena's sunscreen may indeed be broken down by UVA.

Eva Victoria, do you have any data on the stability of the Helioplex formulation? It must be better than nothing as an Avobenzone stabilizer, although I hesitate to rely on the Neutrogena/J&J claims alone. I've seen third party testing data for the UVA blocking ability of a variety of US-available sunscreens, and the best of the Neutrogena Helioplex sunscreens are pretty good for the price. I would like to be able to apply a sunscreen once in the morning, then go about my normal activities, which would involve a few minutes of sun exposure here and there, going from house to car and car to other buildings, but spending the bulk of my time indoors. Reapplication every 2 hours is out of the question, but given the small amount of total irradiance that I'm getting, it doesn't seem like I should have to. Is my logic OK here, or am I missing something? In other words, am I correct in thinking that the stability of a given filter depends on the total dose of UV photons that it receives, rather than the time that it has been on the skin?

It is a bit more complicated than that.
the amount of UV radiation is crucial when it comes to chemical sunscreens. But they tend to sink in the skin after a certain amount of time which (some scientist believe) can damage (by oxidation in the presence of UVR) your skin.
Hence reapplication of chemical filters every 2 h is crucial.

If you don't want to reapply your sunscreen so often esp. during a normal day. I would recommend to use a physical sunscreen. At SPF 15 it would be sufficient protection for your activities and it would not be visible on your skin either.

I'll look into some studies about Helioplex and post it here later.

One more thought: there is actually a TiO2 that does protect up to 385nm. It is engineered at the University of Oxford (UK) and it is called Optisol. It can also be a very good alternative for ZnO.
This is from the studies for Optisol:

"This novel inorganic sunscreen incorporates manganese ions into the structural
lattice of titanium dioxide thereby imparting key functional benefits unparalleled by any standard or coated material commercially available.
Manganese in the bulk – minimizes free radical generation.
Manganese at the surface – provides free radical scavenging."

Eva, I see that some sunscreens from Boots contain the ingredients Optisol. They seem to not want to disclose the ingredient list.
Hard to tell just which ones use it. I believe the Soltan does. Do you have any info. as to which sunscreen from this line is best?
Ebayuk seems to have some pretty good prices. Thanks. Check that.....I see that their Soltan Facial Sun Defense Cream has Optisol in it.

Edited by mustardseed41, 17 April 2010 - 10:58 PM.

[Eva Victoria]

First Neutrogena's sunscreen may indeed be broken down by UVA.

Eva Victoria, do you have any data on the stability of the Helioplex formulation? It must be better than nothing as an Avobenzone stabilizer, although I hesitate to rely on the Neutrogena/J&J claims alone. I've seen third party testing data for the UVA blocking ability of a variety of US-available sunscreens, and the best of the Neutrogena Helioplex sunscreens are pretty good for the price. I would like to be able to apply a sunscreen once in the morning, then go about my normal activities, which would involve a few minutes of sun exposure here and there, going from house to car and car to other buildings, but spending the bulk of my time indoors. Reapplication every 2 hours is out of the question, but given the small amount of total irradiance that I'm getting, it doesn't seem like I should have to. Is my logic OK here, or am I missing something? In other words, am I correct in thinking that the stability of a given filter depends on the total dose of UV photons that it receives, rather than the time that it has been on the skin?

It is a bit more complicated than that.
the amount of UV radiation is crucial when it comes to chemical sunscreens. But they tend to sink in the skin after a certain amount of time which (some scientist believe) can damage (by oxidation in the presence of UVR) your skin.
Hence reapplication of chemical filters every 2 h is crucial.

If you don't want to reapply your sunscreen so often esp. during a normal day. I would recommend to use a physical sunscreen. At SPF 15 it would be sufficient protection for your activities and it would not be visible on your skin either.

I'll look into some studies about Helioplex and post it here later.

One more thought: there is actually a TiO2 that does protect up to 385nm. It is engineered at the University of Oxford (UK) and it is called Optisol. It can also be a very good alternative for ZnO.
This is from the studies for Optisol:

"This novel inorganic sunscreen incorporates manganese ions into the structural
lattice of titanium dioxide thereby imparting key functional benefits unparalleled by any standard or coated material commercially available.
Manganese in the bulk – minimizes free radical generation.
Manganese at the surface – provides free radical scavenging."

Eva, I see that some sunscreens from Boots contain the ingredients Optisol. They seem to not want to disclose the ingredient list.
Hard to tell just which ones use it. I believe the Soltan does. Do you have any info. as to which sunscreen from this line is best?
Ebayuk seems to have some pretty good prices. Thanks. Check that.....I see that their Soltan Facial Sun Defense Cream has Optisol in it.

It is indeed the case. Boots was the first using Optisol in their Soltan sunscreen line.
The higher the SPF the greater the UVA protection of the sunscreen.

But there is another sunscreen that is called Optisol sundefence that has only Optisol.

Soltan products contain OCR, AVO, TiO2 (Optisol), Tinosorb S (if I remember correctly).

Attached Files

•  Optisol_Sundefence.pdf   31.86KB   61 downloads