“Acid” is not typically a word synonymous with hair health – but it should be.
You’ve likely heard of the lemon juice and sunlight trick for lightening hair. When used together, they work to oxidize the pigments in your strands, subtly lightening without bleach or a trip to the salon.
The flip side is that the harsh combination of heat, UV light, and high acidity leaves strands dehydrated and crunchy, not to mention damaged.
Obviously, straight acids like lemon juice are never a good idea. Diluted acids, however, are great news for your hair and scalp.
If you’ve ever experienced issues such as breakage, dullness, frizziness, or dandruff, your hair and scalp might benefit from a pH adjustment.
In this article, you will learn:
- The optimal pH level of your skin, hair and scalp
- Why maintaining the right pH gives you healthier hair
- Why the water from your shower could be damaging your hair
- Why castile soap and baking soda do NOT make good shampoos
- A cheap and easy way to keep your pH level in the optimal range
Table of Contents
- The optimal pH of the skin and scalp
- The optimal pH of the hair shaft
- Why baking soda damages hair
- Why castile soap shouldn’t replace shampoo
- How shower water disrupts the pH of your hair and scalp
- How to regulate the hair and scalp’s pH
- The benefits of a vinegar rinse for hair
- How to do a vinegar rinse properly
- Recipe for a pH-balancing vinegar rinse
- pH-blanaced hair care product recommendations
The optimal pH of the skin and scalp
Depending on the literature, the optimal pH of our skin varies – but we do know that our skin, hair and scalp prefer to be a little bit acidic. On average, the optimal pH of our skin is around 5, but may fall anywhere between the range of 4-6³. This tendency towards acidity preserves the barrier that is referred to as the acid mantle.
The acid mantle, which is maintained by our sebum, encourages a normal, beneficial bacterial flora on the skin’s surface¹. A disruption of this pH not only causes skin barrier issues such as dehydration, but it also allows pathogenic bacteria to thrive¹ ³. These harmful bacteria can contribute to acne and skin disorders such as dandruff and dermatitis⁴ ³.
The optimal pH of the hair shaft
Just like our skin, our hair also has a preferred pH level. The pH of the hair shaft is about 3.67 – and it’s extremely sensitive to the pH of products applied to its surface⁵.
Products that are overly alkaline, such as baking soda and castile soaps, increase the negative electrical charge of the hair⁵. This raises the hair’s cuticle and leads to friction, tangling, and breakage.
Highly alkaline solutions also break down the disulphide bonds of the hair, leading to long term weakening of the strands.
On the contrary, products that are the right pH close the cuticle, reduce friction, and preserve the slip of the hair. Not only does this make the hair less susceptible to damage, but also makes it much shinier and sleeker.
Of course, you can have too much of a good thing. Slight acidity is good, but very acidic solutions are too harsh. If used undiluted, they can cause the hair to break. With a pH of 2, straight lemon juice falls into this category.
Why baking soda damages hair
When diluted in water, baking soda’s pH hovers around 9, which is approximately 50 times more alkaline than the hair’s preferred range. This is one reason why washing your hair with baking soda – as popularized by the “no-poo” hair washing method – is a very bad idea.
That super-soft feeling some get after using baking soda isn’t due to the improved health of their hair. It’s because they are literally breaking down the disulphide bonds of the hair shaft.
Not only does an alkaline pH increase the hair’s negative electrical charge – making breakage far more likely – but it also raises the hair’s cuticle⁵. This allows too much water to penetrate the hair, leading to swelling of the hair shaft⁵.
This repeated swelling, along with the subsequent contraction that occurs as the hair dries, can lead to a kind of damage called hygral fatigue. This can cause the hair to become stretched, causing breakage and damage in the long term.
Typically, the “no-poo” method is followed with an apple cider vinegar rinse to close to cuticle and bring the hair’s pH back to acidity. However, the damage is already done. The hair is not meant to be subjected to such extreme differences in pH. With repeated exposure, even more cumulative damage occurs. Eventually, shampooing with baking soda could cause the hair to become stretched and damaged.
The purveyors of the no-poo method have their hearts in the right place by trying to avoid the chemicals in many conventional hair products. However, it’s easy to find natural, pH-balanced hair products, like the ones recommended below.
If you’re really set on doing the no-poo method, consider using micellar water to cleanse your hair instead of baking soda. Micellar water is a gentle, effective alternative to shampoo. If you’re interested, I have an easy recipe for a DIY micellar cleansing water for hair.
What about castile soap?
Castile soaps are frequently touted as natural alternatives to conventional shampoos. However, soap is alkaline, created by the reaction of bases and fatty acids. Castile soaps are no different, with their pH hovering around a 9. While they’re great for cleansing the body, castile soaps are still much too alkaline for the delicate hair and scalp.
How shower water disrupts the pH of the hair and scalp
The very act of washing your hair can cause low-level damage to your strands. At a neutral pH of approximately 7, shower water is still a lot more alkaline than the hair’s preferred range. As we now know, a disturbed pH makes tangling, friction, and breakage far more likely.
Shower water’s pH is also not ideal for your scalp. Simply washing can disrupt the skin enough to compound issues such as dryness, itching, and dandruff.
Taking this into consideration, it’s not enough to use plain water as the last step in your washing routine. You need something that will lower the pH.
An acidic product should be the last step in your hair washing routine to seal the cuticle and return your hair and scalp to normal pH balance. Ideally, this step shouldn’t even be followed with a rinse.
How to regulate the hair and scalp’s pH
So if plain water won’t cut it, what will?
What you need is a solution that will regulate the pH of both your hair and scalp, that doesn’t need to be rinsed out, and that will leave your hair clean and ready for styling.
The ideal solution is a vinegar rinse.
Properly diluted vinegar will make the cuticle lie flat, leaving your hair softer, shinier, smoother, and easier to manage, no matter your hair type or texture.
Since incorporating regular vinegar rinses, I’ve noticed benefits in the form of less scalp itchiness and softer, more manageable hair. And as someone with bleach-damaged hair that’s prone to frizz, a vinegar rinse also makes my hair dry more smoothly than if I’d just rinsed with plain water.
The benefits of a vinegar rinse for hair:
- Brings the pH of the hair and scalp back to its preferred acidic range, supporting a healthy acid mantle and bacterial flora
- Closes the cuticle, reduces friction, and preserves the slip of the hair, making tangling and breakage less likely
- Helps to relieve itchiness and flaking, which is especially helpful for those with dandruff, dermatitis and psoriasis
- Prolongs the life of your hair colour by sealing the cuticle, preventing dye from escaping
- Aids in balancing oil production on the scalp, depending on your individual needs
- Makes the hair appear shinier by helping the cuticle lie flat
How to do a vinegar rinse properly
Done properly, it’s very safe to do a vinegar rinse at home without professional products (though those can be great, too). But it’s important to be careful. Vinegar is very acidic, and should not under any circumstances be used undiluted, or without proper measuring. Too much vinegar can seriously throw off the pH of your mixture. Be cautious of vinegar rinse recipes that do not specify the pH of the finished product.
I’ve seen recipes that recommend a 1:1 ratio of vinegar to water (or worse – straight vinegar). This is much too acidic for the hair and can lead to breakage and damage. You really don’t need that much vinegar to get a slightly acidic pH.
Many proponents of vinegar rinsing recommend using apple cider vinegar, as it’s less acidic than white vinegar and contains beneficial bacteria. However, apple cider vinegar also has the ability to bring out brassy tones in hair. For someone who likes to bring out the red tones in their hair, this isn’t a problem. But if you prefer to keep your hair colour on the cooler side, such as with some shades of blonde, then white vinegar is more suitable for you.
The ratio of vinegar to water to use for a vinegar rinse
I used pH paper to determine these pH levels. For this reason, I don’t know the exact numbers, but I do know that they’re in the right range for hair and scalp benefits.
Since the preferred pH of the hair shaft is about 3.67, I chose a pH range of 4-4.5 for the rinse. This is a happy medium between the hair and scalp’s preferred ranges that won’t cause damage to your hair.
If you’re using apple cider vinegar:
For a pH of approximately 4-4.5, use 1-2 tsp of apple cider vinegar in 1 cup of water.
If you’re using white vinegar:
For a pH of approximately 4-4.5, use 1/2-1 tsp of white vinegar in 1 cup of water.
There are many possibilities for customization with this recipe. I like to use food-grade culinary waters to dilute my rinse. My favourite is rose water, but I also like orange blossom (neroli) water and mint water, which come with their own benefits.
Benefits of rose water, neroli water and mint water for hair
Rose water: The benefits of rose water don’t stop at its lovely fragrance (which makes your hair smell good for days, by the way) – it also posesses antibacterial and antioxidant properties that are great for your hair, skin and scalp⁶.
Mint water: Peppermint possesses analgesic and cooling properties that are great for soothing an itchy, sensitive scalp. It’s also been shown to stimulate hair growth⁷. I use mint water when my scalp feels irritated or flaky.
Orange blossom/neroli water: Aside from its intoxicating aroma, which is renowned for its uplifting properties, neroli is said to be anti-inflammatory and antibacterial. This makes neroli water beneficial for ailments of all kinds.
If you’d prefer, you can also use plain, distilled water, or at the very least, filtered water. It’s ideal that the water be filtered to prevent any excipients in tap water from messing with the pH of your rinse.
pH-Balancing Vinegar Hair Rinse (Rose, Mint, or Orange Blossom)
What You'll Need
Apple Cider Vinegar Version
White Vinegar Version
- 1 tsp silk amino acids (for extra conditioning)
- 5-10 drops essential oils of your choice (see recipe notes)
- Combine all ingredients in a clean mason jar or glass container of your choice. A glass bottle makes for easier pouring in the shower. Shake well.
- After rinsing out your conditioner, squeeze any excess water from your hair. Pour the vinegar solution over your hair and scalp until completely saturated.
- Let sit for about a minute. Do not rinse out.
- Towel dry and style your hair as usual.
Silk aminos are hydrolyzed proteins derived from the cocoon of the silk worm. Thanks to their low molecular weight, they're capable of penetrating the hair shaft to moisturize and soften your strands. Unlike high molecular weight proteins, silk will not make your hair feel hard or brittle. They're optional, but you can add them if they work for your hair.
Other ways to balance your hair’s pH
Maybe you don’t want an extra step in your hair care routine. I hear you – it’s already complicated enough to choose the right shampoo and conditioner. And if you don’t have any serious hair or scalp woes, why complicate things further?
If you’re really not into rinsing your hair with vinegar, or if you’d just like to take the pH-balancing a step further, there are natural products available formulated with your hair’s pH in mind. These can help to give you the benefits of pH-balacing without adding an extra step to your hair care routine.
pH-balanced hair care product recommendations
AG Hair Natural Remedy Apple Cider Vinegar Leave On Mist
This pH-balacing spray gives you the benefits of vinegar rinsing in a convenient spray. I haven’t used this one personally, but it looks to be one of the cleanest vinegar sprays on the professional market. I’m sensitive, so I don’t love that it contains synthetic fragrance, but the rest of it looks pretty clean.
Where to buy: Amazon
Carina Organics Sweet Pea Dandruff Flake Removal Shampoo
pH-balanced to 5.5-6.5 with apple cider vinegar. I’ve used this one myself, and can attest that it leaves your scalp and hair clean. Has a nice, light scent. Protein-free.
Where to buy: Amazon
Carina Organics Sweet Pea Deep Treatment Conditioner
pH-balanced to 4.5-5.5 with apple cider vinegar. One of the best deep conditioners I’ve ever used, leaving my dry hair soft and manageable. It’s also protein-free, which is great for those with protein-sensitive hair.
Where to buy: Amazon
Carina Organics Sweet Pea Daily Light Conditioner
pH-balanced to 4.5-5.5 with apple cider vinegar. A light, protein-free conditioner that leaves hair soft and moisturized without extra weight. I’ve also used this one myself.
Where to buy: Amazon
Briogeo Rosarco Milk™ Reparative Leave-In Conditioning Spray
According to their website, Briogeo pH-balances all their products to 4.5-5. I’ve never found a leave-in conditioner that makes my hair as smooth and soft-feeling as this one does. Protein free.
The only downside is that the fragrance, while lovely, appears to be synthetic. For that reason, I’m currently looking for a naturally scented leave-in conditioner to replace this product.
Where to buy: Amazon
Carina Organics Sweet Pea Leave In Conditioner
pH-balanced to 4.5-5.5 with apple cider vinegar. I haven’t used this one yet, but it’s not my list to try. A sweet-smelling leave in that conditions without weighing the hair down. Protein-free.
Where to buy: Amazon
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³ Buraczewska, Izabela. “Outside and Inside Skin PH.” Dry Skin and Moisturizers: Chemistry and Function. By Marie Lodén and Howard I. Maibach. Boca Raton: CRC/Taylor & Francis, 2006. 161-69. Print.