chemistry lesson: pH

Many beauty websites refer to the pH of certain products, telling consumers to make sure their product is within a certain range, to understand how that affects your skin, etc. However, unless you’re currently a science major, or are involved in science for a living I doubt you clearly remember the concept of pH that was explained to you in sophomore year chemistry. So I’m here to refresh that concept for you, explain how it affects your skin and which levels certain products should fall under.


how pH is used in cosmetics

what does pH stand for?

pH is a term used in reference to acid/base chemistry that stands for the power of hydrogen, meaning the concentration of hydrogen (H+) atoms present. 

what does pH mean?

Simply put, pH is a way to measure the acidity of an aqueous (water-based) solution. pH is measured on a scale from 0-14. 0-6 indicating the solution is acidic, 7 is neutral, and 8-14 is basic. A commonly used and extremely simple way to measure the pH of a solution is with litmus paper. Litmus paper is an indication strip that can be used in any aqueous solution. Once dipped into the solution the paper will turn a color which correlates to a certain pH. Red/orange is acidic, yellow/green is neutral, and blue/purple is basic. I recently bought a pack of litmus test strips for $5 to test out all my beauty products on (which yes I will be showing in a later post!). 

pH scale reference

image from Chemists Corner

how is pH related to cosmetics?

While there is a lot of complex science involved in the history of pH and its use in formulations, as a consumer there is very little to worry about. In general, skin does not have a pH, it’s a solid, not a solution. However since the skin does have a large water content, the skin mantel can be measured for its acidity. The skin mantel is the outer-most layer of the skin, and once in contact with water droplets, can be measured. However this process cannot be done with litmus paper, typically a probe is used instead to receive a more accurate reading. The skin mantel has been said to have a pH of about 4-6, so a weak acidity. So unless you have extremely sensitive skin, the pH of your products should be around 3-6/7. Luckily formulators know this and nearly every product is created with this in mind. Now you may be asking, what about alpha hydroxy acids? These anti-aging miracle formulas are strong acids (0-3), this is where concentration is important. The concentration of acid in these AHA’s and the amount used in each application is not near enough to damage the skin from the pH perspective. 

pH indicator testing strips_.jpg

So what should take away from all of this? [Major] Cosmetic companies have trained and educated scientists who understand the concept of pH and its application to our skin. Products that claim to be pH balanced are just using that phrase for marketing, as a consumer you should have little to no concern when it comes to the pH of your products. The only instance to be concerned is if you have sensitive skin. An ingredient with a really low pH can be irritating to the skin. 

Out of sheer interest and wanting to help those who are curious also I am planning a weekly pH review of popular products. Hopefully, this can help those out there with very sensitive skin and pretty much anyone else interested in beauty science become better acquainted with the application of pH in cosmetics!

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