Why pH is important in skincare: the skin’s acid mantle

Why pH is important in skincare: the skin’s acid mantle

I’m sure you’ve seen the phrase “pH balanced” on your skincare products and wondered what that actually means. Or maybe you don’t wonder and actually you just slap any ol’thing on your face. I’m here to tell you that it is important and we as consumers should care about the pH of our products.

If you’re not in the mood for a little science… Firstly: What are you doing here? Do I look like a joke to you? Don’t answer that. Secondly: you can skip to the take home message. But, then you’ve made the whole point of my informative blog obsolete… Just saying.

What is pH?

pH is the measure of how basic (alkaline) or acidic something is and is presented as a scale from 0-14. Things that are considered acidic have a lot of H+ ions (hydrogen ions) and things that are basic tend to react with H+ ions. If all the acid and base compounds are “used” up or balanced out, then the pH of the solution is 7, i.e. neutral. Pure water is neutral – as in no added cleaning chemicals or minerals from the earth. The higher the pH, the more basic/alkaline the substance. The lower the pH, the more acidic the substance.

The thing about the pH scale is that it is logarithmic and so its not linear. A solution with pH 8 is not twice as basic as a solution with pH 4. The difference between each reading is actually a factor of 10. This means that the difference between a pH of 4 and 8 is 10x10x10x10 which is 10 000 times different. So a pH of 8 is 10 000 times more basic than a pH of 4. You can imagine why we really need to be paying attention to pH when there is such a significant difference between the values.

Another property to be aware of is pKa. I mean you can be aware of it but I understand if you actually just forget this after reading the paragraph. I’d rather you leave room in your head for pH. pKa values tell you how strongly the hydrogen ion is attached to the acid – how easily it dissociates. In other words how easily the acid molecule lets go of the hydrogen atom. The smaller the pKa, the stronger the acid. This can help to predict the behaviour of the substance; whether its going to lose its hydrogen ions at certain a pH or not.

The acid mantle

The skin has another “layer” above the uppermost layer of skin (the Stratum Corneum) made up of sebum (natural oil secretions), sweat and dead skin cells. I know it sounds gross and bad but actually its the first physical and chemical barrier against the outside world. Its called the acid mantle and its very important. Although its kind of made-up since its not an actual organised layer but rather a concept. Some professionals call the whole system (the gross oil layer and the stratum corneum) the acid mantle.

This layer, regardless of how you think of it, has a pH of between 4.2 and 5.6 so it’s naturally weakly acidic. Enzymes involved in barrier function, the good bacteria and the lipid layer itself function normally in this pH range. When this is disturbed pushed past its buffering capabilities, all hell breaks loose. Not only can you get over-oily or over-dry skin as your body tries to fix the imbalance, but you can introduce pathogens to the skin layers as well as halt important enzymes involved in skin layer repair.

What’s also important to remember is that the skin barrier consists of long chain lipids which means its usually non-polar. This means it repels anything polar or charged and lets more non-polar molecules penetrate deeper (like dissolves like).

Why product pH is important

So now that I’ve explained what it means when we say low pH or high pH, why is this important for skincare products?

  1. If the pH of your product is too high or low, the skin barrier function can be affected. It needs to be in the range your skin can handle or you may find that you upset the balance and you spend extra time and money in vain trying to fix it.
  2. The actives may work differently at higher pH depending on the pKa mentioned before. For instance glycolic acid has more uncharged acid molecules at low pH, meaning it can penetrate the upper layer better. See the pic below for a simplistic explanation.
  3. This means that skincare products with low concentration and low pH can achieve the same effect as a high concentration and high pH product without disturbing the pH balance of the skin.
pH is important yo! Disclaimer – This is simplified. Super low pH would also be bad as the acid molecules would have extra hydrogen ions attached and possibly be positively charged.

Take Home Message

pH is important. Done.

Jokes, there’s more you can do practically. You can buy some cheap pH strips and check your products. Especially those bespoke gluten-free, vegan, all natural products made by your mom’s collegue’s sister’s daughter from left-over fruit ingredients from their farm. This can give you a ball-park figure of the pH of the product. You can also check the labels to see if they either state the pH or mention that the product is pH balanced.

This is especially important if you have dramatic skin like mine that likes to throw a fit with products it doesn’t like. Believe it or not, there are beings walking the earth that don’t have to worry about that. They can just slap anything on their face and its like “Cool, bro. Stoked to try new things”. Those bitches.

References

  1. Skin pH and skin barrier
  2. Lab Muffin video on pH and acids
  3. pH in nature, humans and skin
  4. Impact on barrier function
  5. Kahn academy videos – a nice easy resource to recap forgotten knowledge.

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