Is PFA the same as PPD for sunscreens???
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Thu May 03, 2007 5:19 am

Hello Tsjmom:

I work in the industry and you ask questions that I hear a lot. My view is that to compare products you need to understand what sort of protection measure the manufacturer is giving.

UVB protection measures are standardized as SPF factors. Most people do not realize that SPF only tells you how much the product stops a burn and it tells you absolutely nothing about other protection. Many people mistake a high SPF for being good for everything.

When you get to UVA protection (UVA causes aging), there are 2 main types: physical (or insoluble) sunscreens and chemical (or soluble) sunscreens. Zinc and titanium are physical. Helioplex, Mexoryl and Avobenzone are typical chemical examples. Soluble (chemical) sunscreens are less visible and a good choice for many as they disappear rapidly. But they get used up as they protect from UVA. Essentially Helioplex claims that it lasts longer. Mexoryl works by reinforcing protection around a small band cap (called the short UVA) that is missed out by the standard Avobenzone (Parsol 1789) that is in all these products and that has been around since the 1980s. PFA is not a standardized measure of protection and scientists are not agreed that it’s a good indicator.

Interestingly, when you use physical blocks you do not have the problem of the protecting ingredients breaking down with time (for example the zinc oxide and titanium dioxide literally stay on the top of the skin until wiped or washed off). The absorption spectrums of these ingredients (when used together) give good protection up to 380 nm which means they cover the spectrum that Neutrogena and L'Oreal (the owners of Mexoryl, Anthelios and Lancome) are working to protect. For example, they do not have weak protection from 320 to 345 nm that Mexoryl is used for. Physical sunscreens can be more matte and have good long lasting protection.

I work for PRESCRIBEDsolutions and we work exclusively with dermatologists and other doctors. We have products with both physical and chemical sunscreens. What we have found is that while so many products have focused on UVB and UVA protection, dermatologists and plastic surgeons now realize that this is just not enough for their patients including many undergoing the latest cosmetic procedures who need a product that not only provides UVB and UVA but also visible light protection.

The new PRESCRIBEDsolutions' Up the Anti Full Spectrum and Visible Sunblock SPF 30 was formulated to give comprehensive protection at wavelengths through both the UVA and UVB spectrums upwards to the visible spectrum in a light, tinted cream. Many consumers purchase other products with an SPF 60 or higher without understanding that these may not protect from the type of light that will give them trouble.

So overall,
if you want something more moisturizing you choose a sunscreen with chemical UVA protection. Helioplex, Mexoryl or any of the others shown are fine choices. With all these you will need to reapply.

If you want something longer lasting, use purely physical protection. See how it looks on your skin.

If you have undergone PDT (photodynamic therapy) or other newer cosmetic procedures, or if you have a sensitivity to light such that you get rosacea like redness, then choose a product which also has visible light protection. Prescribed Solutions Up the Anti does this as well as UVA and UVB and has a tint so it doubles as a foundation.

Finally, if you are doing sport or are at the beach, choose something cheap and gunky (so it does not wash off). For everyday choose something more cosmetically elegant.

Mon Aug 27, 2007 7:28 am

UVA rating systems are a little complicated. PPD is known as persistent pigment darkening and measures the protection against tanning much as SPF measures protection against sunburn.
A PFA rating is the ratio of how much more UVA light it takes to cause tanning with a sunscreen as compared to skin without protection. This number is often converted into a + to +++ scale called the PA rating system.

The problem with the PFA rating system is that is provides information about the short wavelength UVA rays (320-approximately 350nm) without providing meaningful information about what is going on from 250-400nm, the longer wavelength UVA rays. These longer wavelength UVA rays do not produce a response that can be observed, but are the cause of solar aging and likely melanoma induction.

The best way to measure protection against these longer wavelength UVA rays is by knowing a products critical wavelength. This is an in-vitro (laboratory test) measuring the point at which a sunscreen protection has dropped to 90%, beginning at the start of the UVB range.
This critical wavelength measurement should be performed on a sample which has been irradiated to prove the formulation is photostable.

The FDA is finally addressing the UVA issue, and is proposing a UVA rating system based both on the PFA and an in-vitro test very similar to critical wavelength. This will be a huge step forward, although it will likely be 2009 at the earliest before these rules take effect.

In the meantime, there are a few products that are photostable with high critical wavelengths (over 375nm) offering excellent UVA protection.
Anthelios makes its critical wavelength of 378nm available on their website for medical professionals. LUCA is a new product which actually put their critical wavelength of 383nm on the bottle. I do not know the exact number
but Neutrogena with Helioplex is likely in the 375nm range. If you like a product and you don't know the critical wavelength, call the manufacturer of sales rep. They can find it out
and the above three are just the ones with which I am familiar.

A quick answer about Mexoryl and Helioplex. Mexoryl is a new active ingredient form L'Oriel. Helioplex is a new stabilizer and strengthener of avobenzone marketed by Neutrogena. These are variations on the same theme, how to increase the critical wavelength and photostabilty of a formulation. Given the close critical wavelength between the two, which is preferable
likely comes down to athetics as they both provide excellent UVA protection.

hope this helps,

k gruber Cool

Mon Aug 27, 2007 4:13 pm

TSJmom,

I wish I could give some broad recommendations, but there are very few products which give their critical wavelength data (although all manufactures have this data as it is used in formulating). Anthelios, LUCA, and Neutrogena with Helioplex definitely meet and exceed the 370nm critical wavelength requirement and are photostable. For Anthelios and LUCA this information is either published on company websites or printed on the bottle. For Neutrogena with Helioplex, I am familiar enough with Helioplex that I am confident that it achieve at least a 375nm critical wavelength and is photostable. Each of these products are very different in athetics, but give comparable UVA protection.

A couple of months ago the EWG (Environmental Working Group) listed sunscreens and level of UVA protection. I have found no mention of their methodology in rating the level of UVA protection. Given the number of products tested, I suspect that they extrapolated their results based on the active ingredients and their concentrations. Unfortunately there is no short cut, you have to do the UVA testing on each individual formulation.

I would suggest if you like a product but don't know the level of UVA protection. Call the company and ask the critical wavelength,PFA, or boots star score. The boots score should be at least 3 stars on a 1-4 scale and the PFA(PA)value should be +++.

This is a competitive market, with expensive products being pushed by doctors and spas. They should know the level of UVA protection (critical wavelength, boots score, and PFA value) of the products they have chosen to represent.
Don't be afraid to ask.

I hope this helps a little,

Kgruber Cool

Thu Aug 30, 2007 5:34 pm

Dear Ms. Kitty,

Thank you for your input.

If I were pushing subjective qualities of a product with which I had financial interest, this relationship should certainly be stated. What I addressed in the site were specific questions, which were directed at a confusing but very important health issue which is the need for good UVA protection and the ability of consumers to make informed decisions about the products they use. To this end, I mentioned three products because they are the only ones which currently provide data on their UVA protection based on in-vitro testing (critical wavelength). This is not a subjective opinion, but fact. If there are other products that provide this information, I will gladly include it in future discussions. By the way, two of the three products mentioned are direct competitors, both in the quality of product they provide and the markets they have targeted.

The only recommendation that I did make was if someone likes a product, ask the manufacturer or sales rep about the level of UVA protection, specifically critical wavelength, PA value or Boots start score as these are the standards for UVA evaluation. Until the FDA approves the new four star UVA rating system, these are the best ways to rate the level of UVA protection provided.

At no time was I concealing my identity, as I provided both my first and last name. Also, absolutely no solicitations have been made on our behalf towards EDS Skin Care. On Monday, while I was googling the FDA website for information regarding their just released UVA regulations including PFA values, I came across the EDS Skin Care website. It was during this time that I came across this website and found questions that I felt I could help answer.

Hope this helps.

Best Regards,

Karl Gruber M.D.
Cool

Wed Sep 12, 2007 5:56 am

h. kitty,

Having a background in physics, and with the terms here coming from that field, maybe the following will help understand these many concepts:

Critical refers to the number at which something stops or starts working. For example, critical mass is the minimum weight after a reaction can take place. The idea is to say that at some exact, particular number the stuff stops working.

Critical wavelength is a difficult concept for sunscreens as there is not one single number (wavelength) at which ingredients stop stopping light. This is partly because all sunscreens have multiple ingredients and even each molecule is just more complex.

Therefore, the discussion above uses 90% of peak absorption. I am not sure if 90% is a good number. It could be. Ideally, I would see a full absorption spectrum for all products from 225 nm to 750nm and then decide depending on what that particular person is most concerned about. That however, is totally impractical.

So, I just recommend you find something you really like the feel of so that you use it each and every day and that you are happy putting a decent amount on your face. Thats most important and will make the biggest difference to you. Don't overdo sun exposure and you will be just fine.

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