Esthetic schools around the country instill the basics on epidermal anatomy and physiology, and the lesson always includes a discussion of the importance of skin pH. For decades we have actually attempted to “balance” the pH of the skin with toners and the like. Do we really have an impact on the skin when we apply acidic or basic topicals? The answers may surprise you.
Understanding pH
The skin’s pH varies from more basic to more acidic as we move from the hypodermis to the stratum corneum. As is typical of this remarkable organ, the inherent design is brilliant and highly protective. First, let’s establish that the pH within the dermis is about 7 and declines to as low as 4.5 near the stratum corneum.
With each layer of the epidermis, the skin’s processes adjust to the environment. Keratinocyte formation prefers a pH of around 6, whereas enzymes in the middle of the epidermis that create our lipid barrier function best at a pH of 5. The common bacteria found on the surface (P. Acnes and S. Epidermidis) of the skin participate in the production of our protective barrier by creating acidic proteins that maintain the pH at the surface around 4.5. While they have no problem surviving if not thriving in those conditions, their actions prevent opportunistic infections from occurring in most cases.
pH And Skin Care
Low pH acids are often used in daily skin care regimens that carry pHs in the 2 to 4 range. What effect does this daily application have on the pH of the skin and how long does it last? Since we know that our bacteria are an actual part of the epidermis, we need to question why we want to harm them.
There is increasing evidence that acne is not a bacterial problem and bacteria live happily and protect us from birth until the day we die. Applying high dose, low pH acids to the skin will harm the “good bacteria,” along with removing lipids and coenocyte layers. Instantly, the skin will drop its outer pH by a modest amount as the blend of the existing pH and the acidic product may temporarily drop the stratum corneum pH to 3.5. This triggers the lower layers (stratum spinosum and stratum granulosum) to increase their lipid production and barrier replacement components. However, by damaging or removing the most acidic portion of the skin, there will be a natural tendency for the skin’s pH to assume the pH of the layers deeper in the epidermis, since the components making up the acidic surface environment have been damaged.
The acids will often be neutralized within minutes and the repair of the stratum corneum becomes the skin’s next priority.
The Problem With Soap
According to research, soaps often have a negative impact by temporarily increasing the pH from 4.5 to 6.6. These changes tell an interesting story. Alkaline soaps (pH 9.5) had an alkalinizing effect on the skin as we might imagine, but the neutral soaps (pH 5.5) also had significant alkalinization. There is an immediate effect from the pH of the solution being put on the skin, but the lasting effect on pH appears to be coming from the disruption of the surface bacteria and lipids.
You would think that the two soaps would be significantly dissimilar because of the pH differences, but instead it was their effect on the epidermis that made the most lasting changes.
Using products closer to a pH of 5 is the most ideal way to maintain good barrier health.
Alkaline Effect On Skin pH
Alkaline water (pH of 8 or higher) has also been shown to change the pH from 4.5 to 6. This reflects the saturation of water into the top layers. If this is not accompanied by scrubbing or a prolonged soak, then the effects may not be that significant. This water absorbs or evaporates fairly quickly, which means the pH likely lasts anywhere from a few minutes to a few hours. Most shower water has a pH of around 7, which is a little better, but it’s easy to see why our skin is dry all the time between water jets and strong soaps.
Typically, it takes the skin one to three days to repair lost lipids and bacteria. Alkaline solutions will temporarily saturate the skin, and this effect lasts a few hours. That is only assuming that we are not stripping the barrier twice daily during recovery. The most important changes that occur, the lasting ones, happen when we overly acidify or alkalinize, resulting in structural changes. It’s clear that most of the products we put on the face should be as close to a pH of 5 as possible to reduce the amount of barrier disruption, improve hydration and skin sensitivity. Cleansers should also be in that pH range. But more importantly, if they are exfoliating in any way, it worsens the pH disruption. Any scrub used on the skin will raise the skin’s pH. Toners, while in many cases alkaline, would only serve to worsen the structural damage (if they are alcohol based) and overly alkalinize the skin.
The takeaway from this conversation is that the skin has many balances and counterbalances to create its complex environment. Making alterations to one aspect of the skin often has ramifications somewhere else. However, it’s clear that using products closer to a pH of 5 is the most ideal way to maintain good barrier health. Remember that a strong barrier means less inflammation from the sun and environmental pollutants, more hydration, less sensitivity and improved appearance. As we acknowledge that bacteria in the gut is very important to digestive health, we too must recognize that bacteria is good for skin health.
