Why the pH of Skin and Products Are Crucially Important

by | Jun 20, 2017 | Acne, Guides | 40 comments

I’ll be honest, the concept of pH is something I neglected and didn’t know about for many many years. Had I been familiar with it I could’ve saved myself from major setbacks, avoided some severe reactionary breakouts, and cured my acne ten times faster.

pH is important for maintaining skin barrier integrity, knowing what products you should never mix, and everything in between. Let’s break down this idea in the simplest way possible so you can start incorporating it to make smarter decisions about your skincare.

Don’t worry, this won’t be like one of those boring chemistry lessons in school or anything. I’ll keep you entertained. 😉

What is pH?

pH stands for the “power of hydrogen” or “potential of hydrogen,” and is the measurement of how concentrated hydrogen ions are in a solution. In simpler terms, it measures how “acidic” or “basic” a substance is in comparison to distilled water which has a “neutral” pH of 7.0. (1)

Anything below a pH of 7.0 is considered an acid, and anything above a pH of 7.0 is considered an alkaline or “basic.” Generally speaking, acids taste sour and bases taste bitter.

Lemon juice, for example, is sour because it contains approximately 5% citric acid which has a pH of 2.2 meaning it’s highly acidic. On the other hand, baking soda taste bitter because it has a pH of 9.0 (highly alkaline). Two things, by the way, that you should NEVER be putting on your face — more about that later.

To further hammer down this point, let’s give some common examples of basic and acidic substances:

  • pH 1 = Battery Acid
  • pH 1.5 – 3.5 = Gastric (Stomach) Acid
  • pH 2 = Lemon Juice
  • pH 3 = Soft Drinks
  • pH 3.4 = Distilled White Vinegar
  • ph 3.5 = Orange Juice
  • pH 4.5 = Beer
  • pH 5.0 = Tea and Coffee
  • pH 5.5 = Rainwater
  • pH 6.2 – 7.4 = Saliva
  • pH 6.8 = Milk
  • *pH 7 = Distilled Water (the focal point of this scale)
  • pH 7.4 = Human Blood
  • pH 9 = Baking Soda
  • pH 9 = Seawater
  • pH 9.0-10.0 = Soaps and Detergents
  • pH 10.5 = Milk of Magnesia
  • pH 11.5 = Household Ammonia
  • pH 12.6 = Household Bleach
  • pH 14 = Lye (Sodium Hydroxide)

Why Does pH Matter For Skincare?

Because the pH of skin influences several factors contributing to its overall health. It’s been demonstrated that skin with pH values below 5.0 are healthier, more hydrated, and have a stronger barrier function than those above 5.0. (2)

Our skin is protected by something called the “acid mantle.” It is a small film on the surface of the stratum corneum composed of fatty acids, lactic acid, pyrrolidine carboxylic acid, amino acids, and a bunch of other sciencey terms and stuff that can be a little overwhelming. Let me translate that to English for normal people.

We have an acid mantle and it kicks ass. Acid mantle = protective barrier on surface of skin composed of sweat, skin oils, and dead skin cells.

This acid mantle is what gives our skin its pH, and ranges anywhere from 4.0 to 7.0, with the average being 4.7. (3) It protects our skin from bacteria, fungi, viruses, environmental pollutants, makes skin soft and supple — it does everything!

Disrupting this lovely skin protector can have adverse effects and lead to stuff like inflammation, atopic dermatitis, dehydrated skin (skin that is both dry and oily at the same time), dry skin, skin sensitivity, acne, malassezia folliculitis etc. (4)

Of equal importance, is the acid mantle’s ability to maintain the integrity of our skin’s moisture barrier and microbiome (i.e. the healthy bacteria that live on our skin).

Just like the bacteria and yeast in our gut that keep us safe from stuff like crohn’s, food sensitivities, autoimmune diseases etc., our skin flora keeps us safe from diseases like acne, rosacea, psoriasis, and dermatitis. (567) Research has shown there is a very close relationship between the pH of skin and having healthy skin bacterium. (89)

What Disrupts Our Skin’s pH and Acid Mantle?

Pollutants, pathogens, excessive occlusion, detergents, soaps, cleansers, heck — even water! (10111213) I can hear you already, “what WATER?!” Now that you’re utterly terrified, let me calm you down and explain. 

Here’s a general rule of thumb: the higher the pH of something, the more disrupting it is to the acid mantle and therefore moisture barrier. So while water isn’t bad per se, “hard water” is. Hard water is simply tap water with a high mineral content causing it to have a pH of 8.5 or more.

Fun-fact: this is why micellar water was invented! Back in the 90s, France was notorious for having “hard water,” so an awesome chemist formulated micellar water so poor french women could clean their faces without nuking their acid mantle.

If you have no idea what micellar water is or want to know how it works, check out this awesome article by the lovely LabMuffin. Cute illustrations included! Let’s continue….

The biggest acid mantle overkill you need to be worrying about is cleanser. You know that super squeaky feeling you get after using one? Yeah, that isn’t good! It’s an indication that your acid mantle has been disrupted. You should be avoiding that super squeaky feeling at all costs!

The goal is to cleanse your skin without over-stripping it of its natural oils. This is a reason the “oil cleansing method” is so popular. It removes debris and gunk, but leaves your face oils alone. Best of all, oils don’t have pH so you don’t gotta worry about alkalinity when choosing which one to use.

The comedogenicity of oils however… well, that’s another story. ~*Insert OCM horror stories here*~

All this is not to say we should stop cleansing altogether for fear of disrupting our acid mantle. In fact, cleansing is important. However, the trick is to use a gentle pH balanced cleanser to maintain our skin barrier’s integrity. A cleanser that is “pH balanced” simply means it has a pH similar to that of skin (4.5-5.5).

Generally speaking, 5.5 is a good number to aim for and doesn’t interfere with skin microflora like alkaline soaps do. (14) Personally, any cleanser higher than pH 6 is a no-go for me. Which brings me to why you should never be putting baking soda on your face….

Baking soda has a pH of 9! Far too alkalizing. Contrary to popular belief, it is often the extremely alkaline substances that cause “chemical burns.” Remember that scene in fight club when Tyler Durden burns the protagonist’s hand? Great film, btw!

Well, that wasn’t an acid: it’s lye (a.k.a. sodium hydroxide). Lye has a pH of 14! It isn’t an acid at all, but a compound on the highest end of the alkalinity scale.

Hold up, wait…. OMG!

YOU. The person reading this right now. WHAT’S THAT THING BEHIND YOU???? Is that lye about to be poured on your face???? QUICK! RUN!

Kidding. Just trying to grab your attention. Like I said, this wasn’t going to be a boring chemistry lesson.

Anyway, alkaline substances (like baking soda) need to be avoided in all skincare routines. Research has shown that using them is very damaging. (15) In fact, there was even this messed up study that tested alkaline products on babies.

They used 2 to 16 week old “infants without skin disease” to see the effect detergents had on them. Those scientist, I tell yuh….

They ended up finding that alkaline soap (9.5 pH) significantly increased the pH of skin (go figure) and concluded that,

“The increase of the skin pH irritates the physiological protective ‘acid mantle’, changes the composition of the cutaneous bacterial flora and the activity of enzymes in the upper epidermis.” (16)

In laymen terms, it f*cks you up. Just kidding. No, but really it does…. To summarize everything we’ve discussed thus far, here’s a quote from a couple dermatologist researchers:

“Skin pH [is] a key factor in barrier homeostasis, stratum corneum integrity, and antimicrobial defense… Recognizing factors that alter skin pH and selecting products that preserve the acid mantle is of prime importance in treating dermatologic patients.” (17)

  • If baking soda is so bad, then why is it in my awesome acne-fighting cleanser that beauty guru recommended?

Good question. Same reason there are so many drugstore products that do diddly squat or damage skin: skincare companies and websites are either stupid, or trying to give people skin problems so they keep buying more stuff. A perfect example is a newly created website called “thankyourskin .com” (Yes, I’m totally throwing shade at it).

The guy running it is only interested in monetary gain, so while he sometimes gives decent advice like “use vitamin C serums” he clearly doesn’t know what he’s talking. Case in point, his stupid article “13 Wonderful Reasons Why You Should Be Using Lemon in Your Beauty Routine.” (More about why lemon is bad in a bit.)

Need more proof he’s a moron? The guy’s blogging about the whole website’s purpose being a $10,000 monthly project: http://www.cloudliving .com/10k-challenge/ — Can you tell I have no respect for these kinds of people?

I’ve said it before: don’t fall prey to the marketing BS out there. There’s a ton of it. Take the time to learn about skincare science, and this stuff becomes blatantly obvious. One pair of skincare researches said it best:

“Most products recommended for sensitive skin have a considerable irritation effect, which is related to the pH of the product. Better regulation of advertisement specifications including the pH level and type of cleanser contained is necessary for the majority of soaps and cleansers.” (18)

  • Wait, so do I need a toner?

It depends. Toners were originally intended to minimize the harsh effects of high pH detergents by dropping the skin pH back down to a healthy equilibrium. However, since the discovery of the ill effects harsh alkaline cleansers have, companies have been formulating their cleansers with lower pHs to do the work a toner is supposed to.

If you’re following the guidelines outlined here and get a pH balanced cleanser (as you should), toner isn’t necessary.

However, there is a whole step in Asian skincare involving the addition of  an “acid toner” after cleanser, but that’s a topic for another time. We’re interested in keeping this pH talk at newbie 101 level.

If all this has been confusing, don’t worry. I gotcho back. Here’s a list of my favorite cleansers, all of which are pH balanced and gentle. If you’d like a longer list, go here.

Accure Sensitive Facial CleanserpH 5.5 Good for sensitive, dry, or normal skin.
Acne.org CleanserpH 5.5Good for combination, normal skin.
CeraVe FoamingpH 5.5.Good for normal to oily skin.
Cosrx Low Ph Good Morning Gel CleanserpH 5.0Good for sensitive, dry, or dehydrated skin. Avoid if you're sensitive to yeast (has saccharomyces ferment).
Hada Labo Tokyo Hydrating Facial CleanserpH 5.5 Good for sensitive, dry, or dehydrated skin.

Now it’s time to have some fun and do a little experiment by going on a pH testing rampage to see where certain items are ranking. It’ll be like a pH jeopardy game! We’ll call it….

What’s the pH of that?

  • Contestant #1

Dr Bronner’s, a.k.a that totally “all natural” stuff those holistic vegan chicks on youtube say you should wash your face with because it’s, you know… “natural” and “free of chemicals.” What does our litmus test have to say about this?

dr bronners castile soap ph

*Buzzer sound*

Ooooooo. Fail. Look at that delicious pH! Completely incompatible with our poor acid mantle. I can hear it crying already, “please! please! get that stuff away from me!” (It does make a good microfiber cloth cleanser though.)

  • Contestant #2

Random hand soap in mother’s kitchen.

Verdict: pH 6. Not bad. Not bad. You raised us well woman!

  • Contestant #3

Baking soda.

baking soda pH

*Buzzer sound*

Atrocious. Absolutely atrocious.

  • Contestant #4

Paula’s Choice Skin Perfecting 8% AHA Gel.

paula's choice AHA gel ph

Verdict: pH 4. Solid.

See what I did there? I purposely tested the last product to prove a point and make a slick transition into the last topic of this article.

pH Dependent Skincare Products.

There are certain ingredients in the skincare world that require specific pHs to work their magic. This is known as pH-dependency. Which products need to be calibrated to a proper pH, you ask? Various active ingredients like chemical exfoliates and serums. Let’s go over a few.

Chemical exfoliates like BHAs (salicylic acid) and AHAs (glycolic, lactic, mandelic) have something called a “Free Acid Value” (FAV), which tells you the true strength of its exfoliating prowess.

When an acid is formulated at a pH below 2.0 the entire percentage of that acid in solution is considered “free” — in other words, completely unrestrained to do everything it’s gonna do like unclog pores, treat acne, slough off dead skin, upregulate collagen production, increase cell turnover etc.

For example, if we have a 20% salicylic acid product at a pH of 2.0, than that entire 20% is “free” to work its magic. However, the closer the pH of that product is raised to 7.0, the less of that total 20% will actually work.

With that said, other than chemical peels you won’t find BHAs and AHAs at drugstores formulated at that low of a pH. While yes, a lower pH means a chemical exfoliant will penetrate more deeply, work more effectively, and have a greater concentrated effect — it’s also more irritating and simply too powerful and dangerous for most newbie skincare purposes.

Could you imagine the horror of teenagers buying chemical peels at drugstores and nonchalantly slathering them on their face, then not knowing what to do next? Gives me anxiety just thinking about it.

So what skincare companies have done (at least the good ones), is decrease the overall acid percentage and slightly raise the pH of products to maintain the acid’s beneficial effects without compromising user safety.

By the way, remember how I said you should never put lemon on your face? Well, the low pH is a reason why. Lemon juice has a pH of 2.0, meaning a free acid value of 5% citric acid which is highly irritating. Oh yeah, and there’s the fact that lemon oil is phototoxic! (19)

Something I made to explain how to use lemons in your skincare routine!

If all of this pH talk has been confusing, overwhelming, or you just want someone to point you in the direction of products that work damn it. Then here’s a cheat sheet with recommended products from amazon to use next time you buy chemical exfoliates or pH-sensitive ingredients. All the products listed here have the proper pH for their respective active ingredients.

Note: included are ingredients like niacinamide that aren’t chemical exfoliates but similarly require a specific pH to work.

AHAs (glycolic acid, lactic acid, mandelic acid)pH = 4 or lowerPC's 8% AHA Gel; Drunk Elephant TLC Framboos Glycolic Night Serum; Silk Natural's 8% AHA Toner; Cosrx AHA 7 Whitehead Power Liquid
Azelaic AcidpH = 4 to 6. 4.9 ideal.GIGI Bioplasma Azelaic Cream 15%; Ecological Formulas Melazepam Cream; 20% Skinoren Cream; 15% Finacea Gel
BHAs (salicylic acid)pH = 4 or lowerPaula's Choice RESIST Daily Pore-Refining Treatment 2% BHA; Paula's Choice Skin Perfecting 2% BHA Liquid; Stridex Strength Medicated Pads; Cosrx BHA Blackhead Power Liquid
NiacinamidepH = 5-7Cosrx Galactomyces 95 Whitening Power Essence; CeraVe Moisturizing Facial Lotion PM; EltaMD UV Clear SPF 46; Mad Hippie Face Cream with Anti Wrinkle Peptide Complex
Retinoids (Tretinoin [requires Rx], Retinol)May be pH dependent (5-6). There's debate about this. Paula's Choice CLINICAL 1% Retinol Treatment with Peptides & Vitamin C for Deep Wrinkles
Vitamin C (SAP)pH = 6-7Mad Hippie Vitamin C Serum
Vitamin C (ascorbic acid)pH = 3-3.5Drunk Elephant C-Firma Day Serum; Timeless Skin Care 20% Vitamin C Plus E Ferulic Acid Serum; [OST] C 20 Original Pure Vitamin C Serum; JJ Lab's Vitamin 20% C Serum; Skinceuticals C E Ferulic; Paula's Choice Resist C15 Super Booster

pH and Wait Times. Are They Necessary?

Because acids work at a specific pH, it’s important that we don’t mix them with other products so they cancel each other out or cause reactionary breakouts.

A general rule of thumb is to wait 20-30 minutes between acids or low pH dependent ingredients before moving on to the next step in your skincare routine. By then, the acid’s pH (below 4.0) has been effectively neutralized by your skin (4.5-5.5).

There’s a bit of disagreement on whether wait times are needed between products. Some skincare companies like Paula’s choice say they are unnecessary altogether, prompting the juicy discussion here.

The video referenced in that post has since been removed removed by Paula’s Choice, which I think is a pretty good indication they might have been wrong on the subject. As cosmetic chemist Stephen Alain Ko said,

[Not using wait times] shows that the acidic solution ‘defeats’ (…obviously) the buffering solution of the moisturizer – if it has one, which means that if you’re using a moisturizer with pH sensitive ingredients a low acidity exfoliator might disrupt the product – IF this interaction occurs on the skin as well.

In other words, using something acidic like a BHA (pH below 4) would neutralize the antioxidant effects of something like Niacinamide (pH 5-7) because an acid trumps the buffering effect a moisturizer would have.

Newbie translation = acids kick more ass than moisturizers. Therefore, acids influence the pH of moisturizers more than moisturizers influence the pH of acids. Don’t mix the two if you want your moisturizer’s ingredients to work.

Order of Skincare Products.

This is the order of a skincare routine with all the things we’ve mentioned being considered. Depending on what products you incorporate, some of these steps won’t apply. Disclaimer: Asian routines include additional steps not included here.

  1. Oil cleansing method, or oil cleanser.
  2. Gentle pH-balanced cleanser (5.5 or below)
  3. Vitamin C (ascorbic acid). Wait 20-30 minutes.
  4. BHA. Wait 20-30 minutes.
  5. AHA (glycolic, lactic, mandelic). Wait 20-30 minutes.
  6. Retinoids (Tretinoin [Retin-A], Retinol)
  7. Spot treatments or other actives (e.g. Benzoyl Peroxide, Azelaic Acid).
  8. Moisturizers.
  9. Occlusives (Vaseline, Aquaphor)

And that does it for pH talk! Hopefully you left this article a more informed skincare-addict citizen.

With love,

—f.c.

Tell your friends to stop using lemon juice! When they ask “why?” Share this!