Shampoo Vs. Soap: What's the Difference?

The other day I was at my local natural foods grocery store and happened to check out the shampoo section. I noticed a new selection of 6 different bars, so of course, I was curious. I was shocked to see that 5 out of 6 of the "shampoo bar" offerings were SOAP!

Too often, I see soap labeled as a "shampoo bar".

This happens at local farmers markets, grocery stores, and all over your favorite large scale internet shopping platforms.

I field objections to solid shampoo often because companies insist on selling soap as shampoo. I can't tell you how many times I've heard, "Oh, I used a shampoo bar before and it made my hair feel like straw." I know instantly it was soap, but I have a series of questions I ask to verify.

The terms "soap" and "shampoo bar" are not interchangeable. They are entirely different things; one is formulated specifically to cleanse and, hopefully, nourish your hair while the other one will absolutely ruin your hair.

In this "Insights from the Alchemist" article, we'll discuss the two motives for this egregious mistake and arm you with three simple ways to distinguish between the two without having to become a cosmetic chemist.

It drives me crazy to see so many soap bars labeled as shampoo, and I often ponder WHY this happens.

While I do not wish to pin a specific motive on any specific company, it comes down to 1) ignorance of cosmetic chemistry or 2) outright deceit.

The Chemistry of Hair

Our hair is very sensitive to changes in pH and likes to remain on the acidic side.

The pH scale measures how acidic or how alkaline a substance is, with 7 being neutral. A measurement of 0 is really acidic, like battery acid, while 14 is the other end of the spectrum, alkaline like lye.

Our hair naturally falls around a pH of 5-5.5 and is able to maintain its integrity when exposed to substances around that range. Water is typically neutral, which means your hair care needs to match the pH of your hair or be slightly more acidic to maintain your hair's structure and the microbiome of the scalp.

Chemistry of Soap

Soap, good 'ole fashioned cold process soap, is by definition an alkaline substance. The chemical process of making soap is FATS + LYE = SOAP. Remember, lye falls on the end of the alkaline spectrum (pH 14). A lye solution will burn your skin just like battery acid. Fats used in soap making, usually vegetable oils, are neutral (pH 7). When those combine, there is a chemical reaction that combines all the lye molecules to all the fat molecules to create a new substance; soap. The resulting soap is ALWAYS alkaline in nature, usually falling around a pH 9. This alkalinity is a required part of the chemical process that binds the lye and fat molecules together. Lowering the pH would break those bonds and you'd just have an oily mess.  Kevin Dun of Scientific Soapmaking has been running an acidic soap challengefor years and has yet to have a successful entry.

What happens when you use an alkaline substance (Soap) on your hair?

Using an alkaline substance, like soap, to wash your hair will cause irreversable damage to your hair over time. After repeated use, you will notice the following things happening to your hair:

• Unable to retain moisture because the cuticles along the hair shaft have been raised
• Increased frizz as the core of the hair strand is unable to stay moisturized so seeks moisture from the atmosphere
• Break down of proteins, causing any natural curl or wave pattern to deteriorate
• Hair dye will be stripped out and will have trouble taking in dye in the future
• Hair feels like straw, because of the increased friction between your strands from the raised cuticles

Despite these negative consequences of using soap on your hair, there are plenty of soap makers who insist soap works and you can find tons of recipes for "shampoo" soap onine. Often, these recipes add an extra oil or butter to claim it as being "formulated" for hair, but as we learned earlier, all oils/butters are nuetral so it would have no effect on bringing the pH down to an acceptable level.

As a soap maker myself, I can understand the desire for soap to work for everything. Soap making is relatively easy to do and a popular hobby for those looking to replace harmful ingredients from their bath time routine. But...... we don't expect our toothpaste to also work as deodorant, so it's time to recognize the chemical differences in needs of our hands, body and hair. Soap is fantastic for your hands and body, which are not as sensitive to the pH change, while your hair will literally be destroyed.

What about companies who KNOW the science, but still market and sell soap as shampoo?

I've had a few conversations over the years with soap makers who do know the chemical differences, but still sell cold process soap labeled as shampoo for various reasons. The most common reasons are (1) The ingredient list for soap is less "scary", so consumers will buy it trying to get away from things they can't pronounce and (2) It's cheaper and easier to produce.

This, in my humble opinion, is just down right dishonest.

It is purposefully misleading. These producers are taking advantage of the consumer's ignorance to sell them a product that is not appropriate for the use for which it is marketed. 

It is knowingly mislabeling. Shampoo is not soap. Soap is not shampoo. It's just factually wrong.

How can you tell the difference without becoming a cosmetic chemist?

1) Price per ounce. Soap is much cheaper and easier to produce. It is typically sold in 3.5-5 oz rectangle or circular bars. If you are looking at a "Shampoo Bar" that is 3.5-5 oz net weight and it is priced under $10, you are looking at a bar of soap. The ingredients to make real shampoo are WAY more expensive than the vegetable oils and lye typically used to make cold process soap. There are exceptions to this; I have seen bars of soap labeled as shampoo sold for prices more comparable to real shampoo, but I have not seen real shampoo sold for prices comparable to soap. This red flag will weed out the majority of those shampoo imposters.

2) Ingredients say "saponified oils of" or list "lye" or "sodium hydroxide" in the ingredients. All of these are indicators that you are looking at soap. "Saponified oils of" is a fancy way of saying the chemical reaction to create soap has taken place between lye and the vegetable oils used. If lye (chemical name: sodium hydroxide) is listed, it is almost positively soap.

Another way you may see the ingredients listed is the combined chemical name of the oil + soap. The most common ones are saponified oils of olive, coconut, castor, and palm. When these oils combine with lye, they actually become something else, so the ingredients may include: sodium olivate, sodium cocoate, castorate, sodium palmate.  

There are no exceptions to this rule, so this red flag will weed out the shampoo imposters.

3) Look for any mention of pH on the package. Shampoo bar manufacturers want you to know you are looking at the real deal. The package will say things like "pH balanced", "color safe", "soap-free". If you are at a local market, ask the maker what the pH of the bar is; if this doesn't get them talking confidently about the difference between soap and shampoo, look elsewhere, they may not understand the question or the chemistry.

Of course, there are many other variables and differences between the ingredients of soap and shampoo, but unless you are interested in becoming a cosmetic formulator yourself, it is cumbersome to learn. These three things are simple rules you can apply to better understand the product in front of you.

If you want to switch to solid shampoo, but feel overwhelmed with the choices out there, check out our line of solid shampoo and conditioner bars. I guarantee you they are pH balanced (5-5.5pH), mild and full of nutritious goodies for your hair.

I hope you learned a little something from this article! This is a topic that I am passionate about, so feel free to ask any questions!