Why does pH matter for hair?
All hair products have a pH. The hair has a pH. The science of hair health, hair care, and salon treatments (dye, bleach, and relaxers) all rely on pH for the best possible outcome. Curly hair, in particular, needs a well-balanced pH to control the cuticle so the hair isn’t fluffy, limp, stiff, brittle, dry, or frizzy.
Because the natural pH of virgin hair is somewhere around 4.5-5.5 it is slightly acidic. Chemical processes will push it from acidic to a more alkaline state. Higher porosity hair (Grade 4-5) can have a more alkaline pH between 8-10.
In this post, I hope you learn how to balance your hair pH correctly, so that you continue to build healthy beautiful hair…let’s dive in.
What is pH?
pH stands for “power of hydrogen” it is a scale used in chemistry to denote the acidity or alkalinity (basicity) of an aqueous solution.
Acidity refers to the amount of acid in a substance, acid is usually a liquid containing hydrogen which can react with other substances to create salts. Acids usually dissolve or burn other substances that they come into contact with. Battery acid is usually the most corrosive substance we think of and stomach acid is next on the list as most acidic.
Alkalinity refers to the opposite end of the pH scale where the substance has a pH higher than 7 when mixed with water and is considered an alkali. Drain cleaner and bleach are considered a high alkaline substances and are highly corrosive.
What is the ideal pH of Hair?
Normal, undyed, undamaged hair has a pH of 4.5 to 5.5.
pH in Hair Products:
A high pH substance opens the hair cuticle and a low pH substance will help smooth and close the cuticle. This is why it is a great idea (if possible) to try an entire line-up of products from one brand. Ideally, they have started with shampoo being slightly more alkaline, and move down to more acidic for conditioner. The leave-in conditioner should reset the pH to normal hair pH. 
Pro tip: Fairy knots happen to be one of the first signs your products are not pH balanced for your hair.
Side Note: pH is unregulated in hair products, but a hair company that knows hair and knows product, will often design their products to have the proper pH for their purpose in your hair routine. For example medicated shampoos are specifically designed to re-balance the pH of your scalp. You can call companies and ask for pH information or you can test the pH yourself if you want to geek out on that.
Shampoo and pH
Shampoo should range between 4 and 8 depending on the job it needs to do. Anti-Dandruff shampoo is usually over 5.5, while children’s shampoo is usually around 7 to prevent tearing. The higher the alkalinity of a shampoo the more frizz you get, because it causes friction between the hair fibers. If you struggle with frizz, check the pH of your shampoo. 
If the pH of your shampoo is under 4 or over 9, I’d ditch it.
We shampoo our hair first to raise the alkalinity and open up the cuticle to drive water in which helps remove buildup and allow the moisture in. If you use shampoo alone, make sure it has a pH that is on the lower side.
Conditioner and pH
Conditioner has a lower pH (usually around 3.5) to return the hair to its normal range; this closes the cuticle back down, sealing in the moisture and filling any gaps in the cuticle. Leave-in should be at the lowest pH in your routine further normalizing and matching the hair pH.
Cowashing and pH
When cowashing alone you risk product buildup and scalp irritation; because the pH is low enough that the cuticle is never opened and water has a harder time getting into the hair shaft to pull impurities. Clarify regularly when cowashing, this will cleanse your scalp and keep you from having blocked follicles.
Using Home Remedies and DIYs that Alter the pH of Your Hair
You want to be careful with home remedies, they are great and easy to use but mixing them and going overboard only increases your likelihood of permanently altering your hair’s pH, which can leave you open to dry hair, damaged hair, discoloring your gray hair permanently, and even chemical haircuts.
How to Remove Semi Permanent Hair Dye Without Bleach: A DIY HAIR WARNING!
If you leave this post with only one take away, I hope I convince you to NEVER mix all these home remedies together and apply them to your hair to remove dye. Any dye that contains the word permanent (semi, demi and permanent) will PERMANENTLY stain your natural color hair. You cannot remove these dyes completely with any home remedy without taking the risk of ruining your hair. At best you will come out with orange hair; at worst, you could severely damage your hair until you grow it all off or cause severe scalp irritations. So please do not mix any of these: dandruff shampoo, baking soda, vitamin c, developer, and whatever else people have put on YouTube to lighten your hair. Every hair stylist I have ever spoken to about this cringes because it can be so damaging.
Porosity and pH:
Low Porosity Hair
On low porosity hair, alkalinity from baking soda washes will help open the cuticle and allow moisture in. Followed with deep conditioner, you can cleanse and rehydrate; a treatment protocol I do about once a month. Acidic products like vitamin C and vinegar will work to tighten the cuticle even more which will dry out low porosity hair.
High Porosity Hair
On high porosity hair, apple cider vinegar rinses will help seal the cuticle and lock in moisture. Protein treatments help fill in the gaps of open cuticles and strengthen the hair. Baking soda can pull all the hydration from your hair and dry it out, so follow with something that brings the pH back down and rehydrates your hair.
High pH Toxicity for Hair
At the highest level of alkalinity is drain cleaner, drain cleaner literally melts hair, which is its job in unclogging drains. One-step down from there (in alkalinity) is hair relaxers and then hair bleach right below that. Alkalizing the hair opens the cuticle and allows the chemical process to alter the color. Too much alkalinity and you melt the hair.
Remember the H in pH? That H stands for hydrogen. Guess what? Hydrogen Peroxide has a high content of hydrogen ions; therefore, it has a high pH of 11. Peroxide is the active ingredient in developer, and the strength of the developer controls how much color is lifted and deposited on the hair.
Peroxide breaks down melanin, that’s why it is used for hair bleach. It is the same reason you have gray hair. Gray hair is caused by the lack of an enzyme called catalase. Normally catalase busts up hydrogen peroxide at the cellular level, but as we age (and some just naturally have less at any age) we slow our production of enzymes. Gray hair is literally caused by the body naturally bleaching out the melanin in the hair. 
What about the pH of water?
Soft Water’s pH
Soft water has a pH of around 6.5, thus it is on the acidic side. Your shampoo and soaps, in general, will lather up more and are a little more difficult to rinse out. You still need conditioner even if the soft water makes your hair feel soft and slippery, because the pH is still above the normal pH of your hair.
You may not need to clarify as often, for mineral buildup like you have with hard water, but your products may be building up if they are not rinsing cleanly away. You want to keep that pH balanced.
Hard Water’s pH
Hard water is rich in minerals, and usually well over a 7.6 pH, thus it is more alkaline. Your shampoo and soaps do not lather as well and generally will rinse away cleanly. Sometimes too cleanly, you need more conditioner because your water is stripping the hair of moisture and building up minerals on the shaft.
You generally need to clarify more frequently with a chelating shampoo to pull the excess minerals. Hard water is drying, and it raises the natural pH of your hair, so always use some form of conditioner in hard water to reset the pH to normal. In some areas you can call your water authority for hard water tests or you can get some simple Hard Water Tests Strips.
Club Soda’s pH
Club soda has a pH of between 4.5 and 5, which is about the normal pH of low porosity hair. Club soda is carbonated water which often contains mineral salts like sodium bicarbonate, sodium citrate, sodium sulfate, potassium sulfate, potassium chloride, disodium phosphate, etc.
It works well for removing “clean product” buildup (since they usually contain water-soluble ingredients), it can be used after a swim to rinse chlorine out of your hair if you can’t shower right away, and as a final rinse if you have hard water and no shower filter to help pull some of the minerals. Added bonus for silver and curls the carbonation fights frizz. 
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Hair pH Balancing Home Recipes to Use Safely:
I recommend you only use one treatment at a time, do not mix them together, and if you choose to try another one, wait a week between treatments with at least one or two normal wash days in between.
Purpose: Baking soda will help open the cuticle up a bit and allow water and cleansers in, this can help to naturally deyellow or clarify silver hair, especially low porosity hair. Do not overdo it, it can dry your hair out if not followed with deep conditioning.
- Use one part baking soda to one part gentle shampoo like Acure Curiously Clarifying Shampoo, mix the baking soda and shampoo thoroughly then apply to your hair gently, avoid the scalp as much as possible.
- Let the mix sit on your hair for a couple of minutes, rinse thoroughly and completely, or shampoo again.
- Follow with a deep conditioner, like Mielle Babassu Oil And Mint Deep Conditioner, leaving it on for 20 minutes under a shower cap with a little heat will help drive the moisture back in.
For short hair, use one-teaspoon baking soda to one-teaspoon shampoo. For long hair, use one-tablespoon to one-tablespoon of each.
Apple Cider Vinegar Rinse:
Purpose: Apple Cider Vinegar can help clarify the hair of mild hard water buildup, it helps smooth the cuticle on porous hair and lock in moisture. Some love the shine and softness it creates. Do not use on your hair either straight or neat, always dilute. Do not use on low porosity hair, it can dry your hair out and make it brittle.
- In a large mixing bowl, add only two tablespoons of Apple Cider Vinegar, and fill the bowl with water in the shower.
- Flip your head over and dunk hair in bowl for about 3-5 minutes swishing it around, dump the remaining liquid on your head after you flip back over.
- Then wash with shampoo and conditioner to rebalance the pH and get rid of the smell.
I only do this about once a year when hard water is getting the better of my curls.
Note: you want to use apple cider vinegar because it is actually loaded with nutrients that help hair and scalp. Plain white vinegar should be reserved for household cleaning; however, in a pinch it will also work but can be harsher.
Purpose: Similar to apple cider vinegar Vitamin C is used as a clarifying. Warning, not great for low porosity hair, and there is a strong metallic smell.
If you feel it is needed:
- Try it by using 1/8 teaspoon or less of pure Vitamin C powder mixed per one cup of water, some use conditioner.
- Soak your hair with the mixture, leave on for a couple of minutes, rinse thoroughly, and follow with a hydrating shampoo and condition.
Purpose: Light clarifying rinse, swimmers rinse, hard water rinse, and defrizzing.
This is easy and safe, get enough to rinse your hair.
- You can leave it all in, you can rinse it out. Up to you but it won’t hurt your hair.
- You can try before shampoo or after conditioner… I would only recommend this as a clarifying treatment, not a daily use.
- Or keep a bottle in your swim bag to do a quick rinse if it will be a while before you can get to your shower.
I hope you found this post educational and helpful.
Thank you for reading. Please feel free to share.
As always it is about so much more than the hair.
If you want, the real science-y stuff on pH check out: pH and Your Hair. A little redox to make you happy. on the Science-y Hair Blog.
Here is a nice list with pH on Science-y Hair Blog, Product pH List
- Walton, Charlene. “Why Your Moisturizer Doesn’t Work.” NaturallyCurly.com, 14 May 2015, naturallycurly.com/curlreading/home/chemist-obia-explains-the-importance-of-ph-balance.
- Gavazzoni Dias MF, de Almeida AM, Cecato PM, Adriano AR, Pichler J. The Shampoo pH can Affect the Hair: Myth or Reality? Int J Trichology. 2014 Jul;6(3):95-9. doi: 10.4103/0974-7753.139078. PMID: 25210332; PMCID: PMC4158629. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4158629/
- Federation of American Societies for Experimental Biology. “Why Hair Turns Gray Is No Longer A Gray Area: Our Hair Bleaches Itself As We Grow Older.” ScienceDaily. ScienceDaily, 24 February 2009. www.sciencedaily.com/releases/2009/02/090223131123.htm.
- Perkins, Sabrina. “Can Club Soda Clarify Your Hair?” NaturallyCurly.com, 24 June 2015, https://www.naturallycurly.com/curlreading/home/can-club-soda-clarify-your-hair
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