Gina wrote:
Could you give some examples of European sunscreens which provide very
significant UVA protection?
Look for a PPD (persistent pigment darkening) rating of
around 30. Two good ones are La Roche Posay Anthelios XL
SPF 60 (PPD 2830) and Bioderma Photoderm Max SPF 100
PPD 30. The most protective formulations will combine
a physical screen (typically titanium dioxide, because it's
less reactive with chemical UVA filters than is zinc oxide)
and several chemical UVA filters (mexoryl sx, mexoryl xl,
and avobenzone), or combine a few of the above with
tinosorb s or m.
You can get them here:
http://www.paraformeplus.com/private/quickbuy.pl [France, shipping is about $15]
The secure server does not work, but this site sells the unscented XL lotion (milk)
http://www.beautycenter.co.uk [Shipping is about $15, maybe more]
Sometimes you can find them on Ebay. Some USA derms
sell them in their offices at 3x the price you can get if you
order overseas.
Second best would be the Canadian formulations: Anthelios L
or Ombrelle SPF 60. They are essentially the same, with a
PPD of about 15. You can get them here:
http://www.feelbest.com
Shipping is about $5
Some of the Asian formulations with PA+++ ratings are
nice and light, but the +++ designation guarantees only
a PPD of 8, which is roughly equivalent to the best that
current FDA regulations on formulations allow in the USA.
This would correspond to a formulation with 3% avobenzone
and 10% octocrylene (Ombrelle SPF 40 or 44 and maybe
a handful of other formulations). It's possible that completely
physical formulations with SPF 30+ could approach a PPD 8 but that's
about the extreme upper limit. If you want significantly greater
UVA protection than that, you have to use chemicals in the formula, too.
My understanding has been that while UVB is burning, it can't enter the
dermis to create oxyradicals that progressively destroy the fibroblasts
necessary for collagen and elastin production.
It does not penetrate as deeply, but it is much more potently
reactive than UVA.
Here is Naylor's comment from the Electronic Textbook
of Dermatology:
http://www.telemedicine.org/sundam/sundam2.4.1.html
"Although UVB makes up only 5% of the ultraviolet photons
reaching the earth's surface, it is the most important component
of sunlight for human skin. It is considered the major action
spectrum for both melanoma and nonmelanoma skin cancer
formation. Although it does not penetrate as deeply as
UVA, and does not interact as vigorously with the epidermis as
UVC, UVB combines depth of penetration and reactivity with
macromolecules in such a way that it is the most biologically
potent portion of the UV spectrum in terms of short and long
term consequences."
He doesn't think UVA more potently photoaging than UVB.
It's hard to argue with him because he has conducted
a clinical trial in photoaging. But, many derms feel that UVA
is very significant, if not more significant, in terms of photoaging.
I believe vitamin C does help regenerate and protect vitamin E in the skin,
and probably vice versa the only successful brand I know of which has
associated C+E together in a serum is made by Primacy.
I would not call Primacy successful. There is no guarantee
of stability with the product. It may be oxidized before
you even open the bottle. If it were fresh, it would be
great, but even then, there is no justification for the price.
Dr. Leslie Baumann has challenged all sellers of topical
ascorbic acid to prove stability. None have responded
to her challenge.
If any one is interested, they also have a sunscreen which uses a patented
technology called SunCaps to encapsulate sunscreen chemicals, allowing them
to push the SPF up to 45 without significantly increasing the likelihood of
irritation (the sunscreen chemicals are supposedly not absorbed into the
skin in large quantities). They also combine this with zinc which they have
managed to make translucent (more patents!). I have tried it and it has a
whiteish shimmer which isn't at all unattractive.
Encaspsulation is great, but their prices are not, nor is the level of
UVA protection that their formulations provide. You can ask them
for the absorbance spectrum or for a PPD rating. They probably
have the information on file, but may or may not give it to you.
Also, each different particle size of zinc oxide (or titanium dioxide,
for that matter) will have a different absorbance spectrum. Carriers
also make a difference. So does the size of the clumps of the
particles. Generally, the smaller the particle, the more translucent
the formulation, and the less UVA protection.
Here is some good reading on UVA protection:
http://www.larocheposay.net/page13.html
Click on the bolded titles for a popup. These two are great:
Suncare product photostability: a key parameter for a more realistic in vitro efficacy
evaluation.
Part I: In vitro efficacy assessment
B.L. Diffey, R.P. Stokes, S. Forestier, C. Mazilier, A. Rougier
Note when reading that the FDA has no requirement for
stability.
Which kind of protection a broad absorption UVA sunscreen provide?
A. Fourtanier, C. Cohen, A. Guéniche, R. Ley, D. Moyal, S. Seité
This is a very great summary of what constitutes excellent
UVA protection.