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Tue Jul 16, 2013 5:52 pm  |
| I have been looking into glycolic acid and sun sensitivity for a while. Perricone believes it is an antioxidant and actually protects your skin with a spf of 2.4. However some new research had indicated that it can actually increase sun damage by 50%. Academy by candy and park Avenue dermatology are some of the people in the "protective" corner. Any thoughts on this. I use aquaglycolic 10% ph 4.4 and am outdoors 10 hours a day. Everything including sunscreen sweats off my face quickly. Should I stop using? Any other evidence out there or first hand experience? Thanks |
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Wed Jul 17, 2013 2:41 am |
| It's common knowledge that ala's increase sun sensitivity. Anything that removes that outer protective layer is going to do that. |
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Wed Jul 17, 2013 4:11 am |
I think skincare can sometimes be like a diet..what works for one person..does not for another.
For me, glycolic worked for getting rid of wrinkles and keeping my dermis thick..but it was always red. I'd be asked if I had rosacea when I'd go get a facial all the time. I used it for years and when I started using retin a and copper peptides the redness was gone. I realized how my skin didn't really like glycolic...and I stay away from it and my skin looks much better. |
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Thu Jul 18, 2013 11:25 pm |
On DermTV, Dr. Neal Schultz says glycolics do not cause photosensitivity. However, I believe that because AHA's cause the skin to exfoliate, this new skin underneath can easily become damaged when exposed to UV.
Suggest you wear a good sunscreen such as Skinceuticals Sport, which has been tested on marathon runners. Even better are the Japanese milk sunscreens - these do not budge and need a cleansing oil to remove. Reapply sunscreen every two hours with a sunscreen spray such as Shigaisen Yoho Make Keep UV Spray. I do a lot of water sports in very hot and humid weather and these products are pretty tenacious. |
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Dry skin but not many wrinkles; 50s and Asian; Topicals: Vit C, tretinoin, hydroquinone & azaleic acid for melasma; Likes: SK-II, Shiseido, Shu Uemura, Skinceuticals, Obagi, P50, Sunday Riley, Hada Labo, facial oils |
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Fri Jul 19, 2013 12:43 am |
I always just thought glycolic acid should be used to repair sunburned skin.
I have read that after 3 weeks of GA treatment, you skin is able to develop a natural barrier against the sun of SPF 2.4. |
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Tue Jul 23, 2013 7:37 am |
After some further research, I have found some interesting facts regarding Acid % and pH. To calculate the FAV (free acid value), use the formula FA = 100 - pH*(3.3*pH+3.13). This will give you the percentage of acid available on your skin. For example, Aqua glycolic face cream (the one I am currently using) is 10% at a pH of 4.4. So, 100 - 4.4*(3.3*4.4+3.13)= 22.34% of the product is available as an acid. Now to find the effective acid concentration, EAC = Concentration * FA/100. So, EAC = 10 * 22.34/100 = 2.234%. Aqua Glycolic face cream only has a free acid value of 2.234% which is basically a moisturizer according to the chart below.
Free Acid Value Effect
0% - 2% Increased moisturization
2% - 4% Smoother, softer skin. Moderate increase in glycosaminoglycans (GAGs).
4% - 8% Moderate increase in squamous cell turnover. Significant increase in GAGs.
8% - 12% Significant increase in squamous cell turnover. Moderate increase in collagen deposition
12% - 15% Significant increase in collagen deposition. Thicker, less fragmented elastic fibers
20% Reversal in basal cell atypia. More uniform melanin pattern
In Conclusion, sun sensitivity probably starts when the free acid value > 4. |
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Tue Jul 23, 2013 9:08 am |
Interesting! Where did you find this?
I'm curious because I use Lactic Acid and want to know how the constants in the FA formula would differ. I suppose the pKa would come into play. Also, I think the general conclusions would differ for AHA's other than Glycolic, also.
And, my apologies because I know this thread is about Glycolic Acid....but..... |
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Tue Jul 23, 2013 9:25 am |
bacchus,
Lactic pKa is 3.86, while glycolic pKa is 3.83. With that said, pKa is only a guideline. For any AHA, when pH = pKa there is 50% free acid available. The formula above will work for lactic as well, but the effect of FAV will change. 4% glycolic FAV will not have the same effect as 4% lactic FAV.
Note: I am not a scientist or skin care professional. These formulas are just from my research because I am a nerd and like to know what I am getting into. |
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