Glycolic acid and pH levels- getting the balance right
It seems that it all comes down to pH balance. As Debbye McGlothen, the CEO of Applied Skin Technology (the company behind Dermagenics) put it:
“Glycolic acid and AHA’s rely on a low pH of about 2 to be effective at drying and peeling the skin. On the other hand, moisturizing products operate in the normal skin pH range of about 5. Moisturizers claiming to have alpha hydroxys and/or glycolic acids in them will actually neutralize the acids, thus rendering the acids inactive. Thus, it becomes more of a marketing issue than a skin health issue. Additionally, there is some gray area as to the efficacy of over use of AHA and glycolics, even at this reduced effectiveness combination.”
A few days later I noticed that Dermaquest advertising that its Glycolic Acid 30% Resurfacer With Stem Cells with this tag: “lower pH increases product efficacy”. It struck me that I should look a bit further into the issue of glycolics and pH levels.
It seems that in addition to the level of glycolic acid, pH also plays a large part in determining the potency of glycolic acid in solution. Physician-strength peels can have a pH as low as 0.6 (strong enough to completely keratolyze the epidermis), while acidities for home peels can be as high as 2.5.
Some companies claim it is possible to raise the to raise the pH of glycolic acid closer to the pH of skin, without compromising its efficacy. For example, VIVITÉ (owned by the Botox company Allergan) says its uses a proprietary buffering process called “partial neutralization”, a technology that is the “result of more than 10 years of scientific study”. I’m not really sure how this works, but VIVITÉ claims that the glycolic acid is released over an extended time period. The only thing I can add to this is that I have tried VIVITÉ and was not impressed by the results.
It seems that most neutralized products range from pH 4 to pH 7. The normal acid mantle of the skin is approximately pH 5.4. I’m not sure what happens to glycolic acid at the 5-6pH level. But I did read (source) that at a pH of 6.2, 85% of the glycolic acid is neutralized. At a pH 7.0, 100% of the glycolic acid is neutralized to salt.
Even the FDA has weighed in on the issue and says that products containing AHAs glycolic and lactic acid are safe for use by consumers if the AHA concentration is 10% or less and the final product has a pH of 3.5 or greater.
Just when I thought I’d got a handle on this, I confusingly found a 1996 study on the effects of glycolic acid at pH levels of 3.25, 3.80, and 4.40, and at 3.25%, 6.50%, 9.75%, and 13.00%. It concluded that: “All pH levels and concentrations demonstrated significant improvement in the condition of the skin with trends implying that increasing the pH increases efficacy.”
When I looked for more studies, I found that typically they looked at the every high (50-70%) concentrations used in chemical peels. One suggested that a pH level below 2 resulted in more “necrosis”, which means premature cell death.
Overall, it seems that pH level does matter. The lower it is, the more likely the glycolic acid product is going to sting and damage cells. The higher the pH level, the more likely the acid will be compromised (at least that seems to be the consensus). So, where possible, look for products that give you information about the pH level as well as the acid concentration so that you can work out what the trade off is before buying something and wondering why it doesn’t work.