We’ve talked a lot about pH on the FutureDerm blog through the years.
The honest answer is, pH matters a lot more than people think. In general, more acidic, or low pH, products provide greater exfoliation and more penetration for the skin, as is the case with vitamin C as L-ascorbic acid (Dermatologic Surgery, 2001). There are some active ingredients, like glycolic acid, that are truly far more effective at lower, more acidic pH levels and far less effective when formulated at higher, more neutral pH levels. In general, as long as your skin can handle it, acids should be kept at acidic levels!
But, at the same time, acidic pH is not a “be all, end all.” A low acidic pH can also cause for ingredients to be more irritating for those with sensitive skin. What’s more, ingredients like zinc oxide and titanium oxide – your mineral or physical sunscreens – have a “pH window” in which their efficacy is optimized. According to FutureDerm chemist Dr. Konstantinos Lahanas, Ph.D., “If the pH of zinc oxide or titanium oxide is too low, the oxides will actually dissolve, leaving you with zero effects. So lowering the pH of mineral sunscreens is not a great idea.” That’s why you rarely see sunscreens with high concentrations of acids, like 10% glycolic acid or salicyclic acid.
Another consideration is that basic pH disrupts the skin’s acid mantle (Dermatology, 1997). Many soaps, detergents, and even shampoos have a basic pH that can strip the skin of essential oils and lipids, leaving it bare and “tight” feeling on your face. For this reason, very rarely, if ever, do I recommend using an ingredient in a formulation at a pH greater than 7.5.
Acidic ingredients, like L-ascorbic acid, glycolic acid, and lactic acid, generally perform better at a lower pH. The lower the pH, the more exfoliating the formulation tends to be – and the deeper the ingredients tend to penetrate.
On the other hand, certain ingredients, like mineral sunscreens zinc or titanium oxide, can’t handle low acidic pH levels. You need a neutral pH for these to function properly, lest they dissolve in solution.
Finally, ingredients formulated at a high/basic pH are generally irritating for the skin’s delicate acid mantle.
So be sure you look for “pH-balanced” in your skin care. This is one of my concerns with natural and organic brands, which often don’t contain buffering systems to keep products in a certain pH range. At any rate, make sure your products read “pH-balanced,” and look for high concentrations of acids if your skin can tolerate it, lower if your skin is sensitive.
Hope this helped! Let me know your skin care questions – write to me at nicki[at]futurederm[dot]com.