When it comes to washing your hair, there's already a lot to think about. From how often to wash your hair, to whether or not to use sulfates, there's a lot going on.
Most of us don't consider even pH, but it really matters. Here's what the right pH for your hair is - and how the wrong shampoo pH can affect your hair.
Shampoo pH: Too often overlooked
When it comes to shampoo, in the last few years it's like we've all become mini hair chemists. We're savvy enough to know that what's on the front of the product label is only part of the story - and we know exactly how to read the ingredients list on the back.
But while sulfate vs sulfate-free shampoo gets discussed all the time, it's like almost everyone's forgotten about shampoo pH. And unlike the ingredients, this is one important factor that is hardly ever written on a shampoo label.
That's too bad, because your shampoo's pH is one of the things that most affects your hair. It has a powerful impact on the way your strands behave and even how other products interact with your hair and scalp. The pH is just as, if not more important, than whether there are sulfates in your shampoo or not.
Knowing the effects of pH on your hair also shows definitively why doing crazy things like using baking soda to wash your hair is a bad idea indeed.
So here's exactly what scientists have discovered and some steps you can take personally to insure your hair against pH damage.
The pH of your shampoo has a strong effect on hair, but is rarely listed on product labels.
What hadn't been done until very recently, was a thorough analysis of the pH levels of different shampoos on themarket, to see exactly how exposed we are to high pH levels from this beauty staple.
A team of researchers in Brazil decided to take up that challenge. They bought up 125 different shampoos and tested their pHs.
The researchers looked at everything from professional salon shampoos, to dermatological prescription-only formulas, to the multinational brands you'll see on pretty much every supermarket shelf, and in hair stores and pharmacies the world over.
The results were pretty shocking. Very, very few of the shampoos available were pH-balanced. The overwhelming majority of the shampoos had a high pH; way too high to be safe for your hair.
So what is a pH-balanced shampoo?
Let's back up and get clear on what exactly a pH balanced shampoo is, so we can see exactly how off the charts some shampoo pHs can be.
An important thing to remember is that "pH balanced" depends on which part of your body we're talking about.
The pH scale runs from 1-14, with 1 being really acidic and 14 being really alkaline. 7, right up in the middle of that, is typically considered neutral. It's a great pH for your eye area (which is why the tear-free baby shampoo formulas are right around that pH).
A product that's pH-balanced for your skin should be at around the 5.5 level. But your hair is different.
The natural pH of hair is acidic, unlike many shampoos. Image by Houcine Ncib.
What is the pH of hair?
The pH of hair is 3.67. Your hair is an acidic place to be and ideally, your shampoos would match that.
Instead, as the Brazilian study found, most shampoos are way more alkaline. And that means they actively damage your hair and can make it harder to deal with.
How does shampoo pH affect your hair?
Your hair is very, very sensitive to changes in pH. Any product you apply to your hair that has a pH higher than 3.67 is going to increase the negativity of your hair's electric network (yes, your hair does have its very own electric network).
High pH in shampoos increases frizz and tangles
That increase in negativity shows up as static electricity, which makes your strands start to repel each other, which in turn creates the phenomenon we all know as frizz.
More static also means more friction between your hair fibres, which is not a good thing.
High pH in your shampoo makes your hair prone to static, breakage and tangles. Image by Gregory Pappos.
High pH increases the risk of hair damage
All that interfiber friction which comes courtesy of the high alkaline, static-inducing effect has worse consequences than a little frizz. It's actually damaging to the hair.
Countless studies have shown that friction leads to tangles, cuticle damage and hair breakage - and this is multiplied on curly hair especially tightly curled hair. This is how it happens:
The static-friction-frizz cycle
The static-creation process begins earlier than you might think. As soon as you rinse your hair with water (pH of 7), your hair already starts to pick up a negative charge.
Then, when you add shampoo, it goes up again: most shampoos aren't just alkaline, they're based on cleansers which are anionic or negatively-charged, which adds to the negative charge load.
The higher this load rises, the more the static and interfibre friction increase, creating more tangles and damage at the strand level, which in turn raise the negative charge of your hair in a vicious cycle.
It's all this negativity that makes your hair harder to deal with after using a high pH shampoo - more static, more frizz, and more tangles - and easier to break.
How does shampoo pH affect your scalp?
When you use a shampoo with a high pH, it increases the pH of your scalp. As your scalp pH goes up, your skin becomes dehydrated and your natural bacterial flora are altered.
This shift can make your skin more prone to infection and irritation, especially if you have sensitive skin. If you tend to get scalp acne, the high pH can sometimes worsen your condition, due to the changes in bacteria on your scalp.
Are salon shampoos better than cheap drugstore shampoos?
There's always a debate about whether pricier salon shampoos are better than cheaper supermarket options. When it comes to shampoo pH, the evidence from this study weighs in favour of salon cleansers.
75% of the salon shampoos in the study had a low pH (categorised by the researchers as under 5.5). That compares to just 34% of popular, mainstream brands.
Whether a specific salon shampoo is better than a specific drugstore or supermarket shampoo will depend on the pH of both shampoos, plus all the other factors that make a good shampoo.
Nonetheless, the statistics indicate you have twice the chance of ending up with a shampoo that has a damaging pH if you go for the cheaper option.
Prescription shampoos: High pH or low pH?
Dermatologists and trichologists are the most trusted professionals when it comes to haircare. They have a scientific understanding of hair that cuts through the crazy hair trends on the Internet and surpasses the experience of hairdressers IRL.
So it was a surprise to see that the formulas they prescribe to treat scalp conditions - everything from psoriasis to dandruff to alopecia - tended to come in with high pHs. The average pH of prescription shampoos in the study was even higher than the mainstream, middle-of- the-market shampoos you'd pick up in the cosmetics aisle at the supermarket.
On average, 59.5 % of shampoos prescribed by derms had a high pH - one as high as 9.
Shampoo pH: The hair-scalp conundrum
You might have noticed that while your hair's pH is about 3.67, the ideal pH for the scalp is 5.5 - just like the skin all over your body. This creates a bit of a dilemma, since it means that what's best for the scalp is very different from what's best for the hair.
This goes some way to explaining why derma-prescribed shampoos tend to be the worst on the hair. Like the study authors say, "Little is taught in medical schools about hair cosmetics." As a result, prescription haircare products "are based only on the active substance for the treatment of the scalp and usually disregard the hair fibre structure."
Ironically, a lot of the dermatological shampoos tested were prescribed for hair growth, but were actually capable of causing significant damage to the hair shaft, thanks to their high pHs.
Damaged hair that breaks off easily can make any growth effects created on the scalp less noticeable for patients - especially if they happen to have tightly-curled hair which is already more prone to breakage at the ends.
So what shampoo pH is good for your hair and scalp?
The shampoo with the right pH for your scalp might not be right for your hair. Image by Craig Adderley.
Since there actually isn't a standardised pH for shampoos, the researchers chose 5.5 and lower as their benchmark for a low pH shampoo.
A pH of 5.5 keeps the scalp - source of the hair - happy and healthy without taking the hair too far away from its preferred 3.67.
While this is a start, in a perfect world your shampoo wouldn't just be able to clean or treat the scalp. It would be formulated to respect your hair's pH and even enhance your hair's softness, strand alignment and natural shine, too.
This isn't as far off as it sounds: one shampoo in the study had a pH very close to your hair's natural pH. The researchers are calling for more product development like this and hopefully more and more formulators will be taking heed.