Skincare Chemistry: All You Need to Know about pH

This post is by reader request.  One of my favorite chemistry topics!  Let’s jump right in.  I won’t bore you with all the details, just some basic chemistry.

pH is simple.  It’s a way of measuring how acidic or alkaline (also known as basic) a substance is.  This is done by measuring how much H+, hydrogen ion, is present in a solution.

When levels of H+ are low, you have a basic or alkaline substance.  When levels of H+ are high, you have an acidic substance.  Pure water is neither acidic nor alkaline; it’s neutral. A pH of 7 is neutral and it’s the midpoint of the scale.  As you get farther from the midpoint, the substance becomes more acidic as the numbers go down and more alkaline (basic) as the numbers go up.

Because of the logarithmic nature of this scale, each change in pH is equivalent to a tenfold change in H+ concentration.  That means that a substance with a pH of 2 is 10 times more acidic than something with a pH of 3, 100 times more acidic than a pH of 4, 1,000 times more acidic than a substance with a pH of 5, and so on.  By the time you reach a pH of 14, the H+ concentration is VERY low, making it extremely basic instead of acidic.  At a pH of 1, the H+ concentration is exceedingly high and so you have something extremely acidic.

That’s all you really need to know for this post.  Here’s a graphic for all my visual learners 🙂

ph scale 1

So what does this have to do with skincare, right?

“pH balanced”

It’s true that the skin (and hair too) is naturally acidic, usually with a pH between 4 and 6.  The outer layer where the pH of skin is fairly low is often called the “acid mantle.”  When this layer of the skin stays within its proper acidic pH range, it prevents dryness and weaknesses in the skin where bacteria can enter and cause pimples and stuff.  Of course, you should not use products that are highly acidic on your skin since a very low pH is corrosive and can burn the skin.  At the same time, using extremely alkaline products would be dangerous too due to their caustic nature and ability to dissolve skin (doesn’t sound pleasant, does it?).

Most soaps and products that clean are quite basic.  Using an alkaline product would raise the pH of the outer layer of your skin, likely disrupting the acid mantle.  Most people’s skin can bounce back from this relatively quickly.  In some instances, such as very sensitive or acne-prone skin, the skin might need some help. When I was pregnant and my skin was especially oily and sensitive, I was very aware of pH.  I tried to use as few alkaline products as I could, keeping most of my products neutral or acidic.

If you find that your skin is sensitive to pH, here’s what I recommend (of course, I am not a dermatologist!):

  • Use a cleanser that has a pH of about 8.  You can also consider using a cleanser that is closer to neutral.
  • Use an acidic toner after cleansing to help restore the acid mantle as quickly as possible.
  • Use a neutral or slightly acidic moisturizer.

If your skin is already irritated and dry from problems with pH, avoid all acidic products until you’ve healed up.  Only use very slightly alkaline and neutral products since acid will almost certainly sting and cause more damage and dryness.

In the end, the term “pH balanced” is just a marketing ploy to get you to buy stuff.  Cosmetic companies just assume that you don’t know what it means and that you’ll just buy what they’re selling because it’s “pH balanced.” Now that you know what it is, though, you can make your own stuff that meets your needs.

How to determine pH

The only way to know the pH of something is to test it out with an indicator.  Indicators are substances that change color depending on the pH of its environment.  There are many indicators but the most convenient one is pH paper.  Find a bunch on Amazon here.  You dip pH paper, or hydrion paper, into what you want to test and match up the color to find the corresponding approximate pH range.  They’re okay as far as accuracy goes, good enough for what we need.  Beware though — don’t use litmus paper.  Litmus paper only tells you if something is an acid or a base but it does not give a precise pH value.

If you’re very serious about pH and want very accurate and precise measurements, think about purchasing  a pH meter.  Good ones aren’t cheap.

Reasons to determine pH

When I make soap, pH papers are invaluable because using a soap before it’s ready can cause serious skin irritation, itching, and even burns.  Usually, I’ll put a few drops of water onto the soap, make sure a small amount of soap dissolves, then dip the paper into the very small puddle of water on the bar of soap.  When the pH is between 8 and 10, it’s a usable soap.

Some preservatives are rendered ineffective by pH.  The preservative I usually use, Optiphen, is effective between pH 4 and pH 8.  Lotions and creams I make never go beyond this range so I’m safe.  Check the manufacturer of your favorite preservative to see what the effective pH range is.  Be aware that using preservatives outside the recommended pH range can make them less effective or not work at all.

Ways to lower pH

Most of the time, DIYers want to lower the pH of their products to make them more in line with the pH of the acid mantle.  When adding any of the suggestions listed below, be sure to dilute and add small amounts at a time.  It’s better to add too little and just add more if necessary.  Add a little, test it out.

  • add citric acid — citric acid is commonly used for the sole purpose of lowering pH, not my favorite choice but has some preservative qualities which is nice
  • add vitamin C — vitamin C has some great benefits for skin plus it’s pretty cheap so I prefer using this to lower pH of cleansers and toners
  • add AHA, alpha hydroxy acid — also has good benefits for skin, as I’m sure you’ve seen before.  This is a good choice for older skin and for people who do not spend much time in the sun.  This is also the better choice for creams and lotions, in my opinion.

If you need to raise the pH of your product, sodium hydroxide is usually the choice.  Sometimes you will see sodium hydroxide on an ingredient list.  This is off-putting because sodium hydroxide is lye, with an extremely high pH, and is often used as drain cleaner.  However, it’s usually present just to raise pH.

Final thoughts on pH

pH is important but it’s even more important if your skin is sensitive or prone to breakouts.  I don’t monitor pH very closely because most of my products are close to neutral.  The cleanser I make and use religiously is right around 8, the scrub I prefer is between 4 and 5, and my moisturizer/oil blend is basically neutral.  My skin bounces back quickly from small changes to the acid mantle but if I switch to soap, with a pH of 9 or 10, my skin will inevitably break out.  If you find yourself breaking out a lot or having a lot of redness and irritation, consider lowering the pH of the products you use.

I plan on incorporating an acidic toner into my regimen so keep your eyes open for that recipe coming soon.

This post is pinned to my Homemade Skincare board.  Check it out.  There’s some good stuff pinned there and I’ll be pinning more.

Questions?  Comments?  Email  I always answer and sometimes I post Q&A here on the blog.

4 thoughts on “Skincare Chemistry: All You Need to Know about pH

  1. Pingback: Homemade Face Cleanser | hippie brown girl

  2. Pingback: Make Your Own Lotion: Preservatives | hippie brown girl

  3. Pingback: Make Your Own Lotion: Preservatives | hippie brown girl

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