The Shampoo Bar Con, Hair and pH

shampoo bar  without wrapping
Photo by Tabitha Mort from Pexels

Shampoo bars are great – they have minimal packaging (yay for the planet) and are perfect for reducing liquid items when you air-travel (yay for me). I concede this may not be a high priority for the time being, but in a brighter, more carefree and more Covid-free future we may once more choose to (or have to) make use of airplanes and worry about whether to pack that shampoo bottle or not. Somewhat scandalously, however, a lot of what gets advertised as shampoo bars are actually just fancy, over-priced soap bars. This may not be a problem for you, unless – like me – you have fine (long) hair, sensitive skin, live in a hard water area and you dislike being taken for a fool and tricked out of your hard-earned money. Let me explain …

The difference between soap and shampoo

The difference between soap and shampoo generally is the cleaning agent used. Commercial shampoos use detergents, usually sodium lauryl sulfate (SLS) – the same cleaning agent that is used in washing-up liquid or dish soap and clothes detergent. Soaps get their cleaning agent “soap” from “saponification” – a reaction between oils and lye (sodium or potassium hydroxide). You can see where the terminology already gets confusing.

Both soap and SLS are powerful degreasers but they may not be the best choice for people who have sensitive skin or fine hair. Sodium lauryl sulfate is known to be irritating to skin (its molecules are so small that they can penetrate the skin’s top layer and wreak havoc on the skin’s chemistry and structure) and can leave skin too clean. Eventually skin will dry out and crack, as you may experience after washing the dishes without gloves on too many times.

The trouble with pH

Another difference between shampoo and soap is their pH. pH tells you whether a liquid (or dissolved) substance is in the acidic (sour) or alkaline (basic) range. Lemon juice for example, typically has a pH of around 2 and sodium hydroxide lye, which is used in soap making, has a pH of about 14, water has a pH of 7 and is considered neutral. Either extremes on the spectrum should be avoided as both are extremely corrosive.

corroded metal pipes
Your hair will look like this if you expose it to pH 1 or pH 14. Just kidding. You’ll no longer have hair – or skin. (Photo by pisauikan on Unsplash)

You may know that face and body washes generally have a disclaimer assuring you they are “pH skin neutral”. Skin’s natural pH is around 5 and these products will match that. Shampoos are usually formulated to do the same but this is not possible for soap. Soap’s natural pH lies in the 8-10 range and usually a soap that claims to be more skin-friendly just contains more oil to make it slightly less stripping.

What happens when hair is exposed to a “shampoo bar” that’s actually a soap bar with a pH around 8 is that the core of the hair shaft absorbs more water, causing it to swell, and the cuticle layer can become damaged by being stretched beyond its capacity. Once the cuticle is damaged, hair is more prone to drying out and breaking. This is a particular problem for fine hair as it tends to be more fragile anyway; it may not be a problem for thicker hair strands.

Apart from that, soap and hard water mix to make a mess. When the calcium and magnesium ions from hard water react with soap, they form scum. This is notoriously annoying to remove and can build up on hair, leaving it with a tacky feeling and becoming unmanageable (this may affect thicker hair too).

What on earth are syndet bars? And why you might want one…

There is light at the end of the tunnel, though: shampoo bars with the correct pH do exist and are sometimes called syndet (synthetic detergent) bars. Unfortunately, as long as these are still made with sodium lauryl sulfate, there is a good chance that they are just as drying as standard shampoo.

hands holding coconut halves
Photo by cottonbro from Pexels

However, this is where we get to the interesting part. There is a new generation of syndet bars out there, which incorporate gentler cleansers such as sodium cocoyl isethionate. Sodium cocoyl isethionate is widely considered to be one of the gentlest cleansers out there. Also, despite being referred to as a synthetic cleaning agent, it is actually derived from coconuts. 

Personally, I love the shampoo bars from FizzyFuzzy, which contain some hair-loving ingredients beyond the basics, such as pro-vitamin B5 and proteins, which help with moisture retention and elasticity:

I also like Lamazuna bars, which can be purchased here:

How to shop for shampoo bars

It’s not always easy to tell whether a bar is a soap bar or a proper shampoo bar especially when shopping from small artisan producers. If in doubt, ask whether they use saponification and look at the ingredients. If a bar only seems to list oils (even when they are all plant derived and organic) chances are that it is, in fact, a soap bar. The same goes if the ingredients listing has the below:

sodium [something-]ate – e.g. sodium laurate, sodium cocoate, sodium tallowate


Synthetic cleansers to look for instead:

  • cocoamidopropyl betaine (CAPB)
  • sodium cocoyl isethionate
  • alkyl sulfosuccinates ([something] succinate in an ingredients list)
  • alkyl sarcosinates


Finally, just a note on baby shampoo: when it says “as gentle as water” that is because it has the pH of water, which is 7 and not optimal for hair and scalp. This might not be an issue for occasional use but for those washing their hair frequently and those with fine hair an adult-formulated shampoo with gentle cleansers would almost certainly be better. 

Happy hair washing!

woman flicking wet hair back
Photo by Armin Rimoldi from Pexels


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