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  • Writer's pictureLindsey Nelson

Decoding Haircare: Understanding the Chemistry Behind Shampoo and Conditioner Ingredients

Lindsey Nelson unlocks the secrets behind the chemistry of the ingredients in haircare.

Have you ever looked at the ingredients label on the back of a shampoo or conditioner bottle?

Do you know what any of those "sciencey" words are, let alone how to pronounce them?

Don't worry! Most people have no clue what any of those words are!

In this blog, we are going to do a deep dive into understanding what ingredients are in your favorite shampoos and conditioners.

One thing I'd like to mention is that I am not a cosmetic chemist, but I will do my best to help you understand these ingredients and their purpose.

An important thing to remember is that I am still learning about this topic, and I will edit this post when I learn something new or as new information comes out.

Lindsey Nelson explains the chemistry behind shampoo and conditioner ingredients

Hair Anatomy 101: Science of Hair Structure

Today, we are going to go back in time to when we were all in Chemistry class.

For most of you, including myself, it's been a long time, so I'll go slow!

I promise you, all of this will come together in the end.

Lindsey Nelson explains our hair structure.

The hair on our heads is called terminal hair, and this particualr hair contains what is called a medulla. 

Our hair has three layers: the medulla, the cortex, and the cuticle.

The medulla is located deep in the middle of the hair shaft and is composed of proteins.

Surrounding the medulla is another layer of the hair shaft called the cortex, which is the star of our hair.

In the cortex, there are cells such as hard keratin, lipids, and proteins, and disulfide (sulfur) bonds hold all of this together.

Also, in the cortex, we have melanin, which gives our hair its pigment.

There are two types of melanin: eumelanin, which is brown to black pigment, and pheomelanin, which is yellow-red to red pigment.

Traveling away from the center of the hair, the outermost layer of the hair shaft is the cuticle. 

The cuticle is probably the term that you have heard of the most because it is the layer of the hair shaft that we deal with on a daily basis.

The cuticle has a "scale-like" covering that serves as a layer of protection and helps repel water.

The cuticle protects the cortex from damage, but over time, the cuticle may become damaged, too.

This can be caused in a number of different ways: aggressive brushing, too much heat, chemical damage, or neglecting your hair in general.

Using heat protectants, low-pH hair products, and proper home care, all help protect our hair's fragile cuticles. 

Maintaining Healthy Hair: Understanding the Role of pH in Cuticle Protection

In order for us to understand why certain ingredients are in our hair shampoos and conditioners, we first have to understand the pH scale.

The pH scale indicates if a liquid is acidic, neutral, or alkaline.

The scale ranges from 0, being a very strong acid, to 14, being a very strong alkaline, and a 7 being neutral.

The pH scale also has to do with ions and their electrical charges, but I am not going to bore you with too much Chemistry talk.

Hair lives at a 4.5-5.5 of the pH scale
Hair lives at a 4.5-5.5 of the pH scale

Our hair has a pH of 4.5-5.5, and when we use chemicals that have a high pH to color or highlight our hair, the scale-like layers of the cuticle lift open.

The cuticle opens up to allow a permanent change to happen within the cortex layer of the hair shaft.

Even when we wash our hair with water, which has a pH of 7, we slightly swell the cuticle.

The cuticle, which is the cortex's protective barrier, prevents it from drying out.

So, when the cuticle is opened, the protective barrier is stripped away.

Closing down the hair's cuticle is the only way to prevent further over-drying and potential breakage or damage.

How do we close down the hair's cuticle?

By using a solution (shampoo, conditioner, or treatments) with a low pH.

Using acidic hair treatments helps close the cuticles so our hair stays healthy, shiny, and strong.

An excellent way to imagine this is to picture the scales on a snake.

When the cuticle layer is perfectly tight, and in line, the snake repels water and is able to protect itself.

Now, if some of those scales are lifted or missing, the snake's protective barrier would be compromised.

The same concept is true for our hair.

A lifted, open cuticle is more susceptible to damage than a closed-down cuticle.

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Protecting Your Hair: The Impact of Water and pH in Cuticle Swelling

Remember what I said earlier about water swelling the cuticle?

Every time we wash our hair or even get it wet, we slightly swell our hair's cuticle.

This is unavoidable because we have to wash our hair, but we can be aware of what we are shampooing with in order to take better care of our hair.

Companies tend to use ingredients with a lower pH to help close the cuticle, preventing drying or any damage.

Decoding the Ingredients in Hair Shampoo and Conditioner

The shampoo and conditioner we use have a long list of ingredients, and they all have their job to do, but the star players are the following:

Aqua- All shampoos need water to keep the ingredients dissolved. Water serves as a solvent and is typically between 45%-75% of the bottle's content. 

Surfactants- These are the detergents that clean away dead skin cells, dirt, sebum, pollen, and other environmental contaminants. 

Most shampoos contain blends of 3-4 different surfactants. 

You may assume a surfactant is doing a great job by how much lathering it produces, but that is only sometimes the case. 

Some gentle sulfate-free surfactants do not provide much foam at all and still do a great job cleansing the scalp and hair. 

Examples of surfactants are Sodium lauryl sulfatesodium laureth sulfateammonium laureth sulfate, and disodium laureth sulfosuccinate (sulfate-free). 

Humectants- These ingredients are used to hydrate or add moisture to the hair.

They also attract water molecules from the environment, trapping moisture inside the hair. 

Humectants can make the hair feel softer, more bouncy, more elastic, and less brittle

Panthenol serves as a humectant by adding moisture and helping the hair retain it as well, but it also helps improve shine

 Examples of humectants are glycerinpanthenolaloe verahyaluronic acid, peptidespropylene glycol, and honey

Acids- Acids nourish the scalp and can help to hydrate it, revitalize hair, boost its ability to hold on to moisture, and improve its texture

They also serve as pH adjusters, which lower the pH of the hair and close down the cuticle. 

Some acids serve multiple purposes and may help exfoliate the scalp, reduce dandruff, and promote hair growth. 

Lindsey Nelson explains what all the ingredients are in a bottle of shampoo

Examples of acids are citric acidhyaluronic acidsalicylic acid, and lactic acid.

Silicones- These ingredients are mainly added to conditioners and treatments. They give a nice glide when detangling wet hair, provide anti-frizz properties, and weigh the hair down.

Silicones form a barrier seal around the hair, which keeps it hydrated and frizz-free.

Silicones can cause build-up on the hair, so they have gotten a bad reputation over the years.

In order to remove any silicone build-up, specific clarifying shampoos or professional treatments are required. 

The easiest way to identify silicones is to look for words that end in one of these: –cone, –conol, –silane, or –siloxane.

Note that some conditioners and treatments do not contain silicones and use an alternative ingredient. 

More brands are becoming aware of their customers' concerns and are slowly removing silicones from their products. 

Examples of silicones used are dimethiconeamodimthicone, or cyclomethicone

Viscosity builders- With so much water used in hair products, product thickeners are used to keep the product from being too thin and watery. 

Some thickeners, such as glycol distearate, also help add moisture. 

Examples of viscosity builders are sodium chloride, glycol distearate, and ammonium chloride.

Preservatives- Cosmetic chemists add preservatives to hair products in order to keep bacteria, mold, fungi, and yeast out of the product. 

Some sort of preservative is necessary, whether it is synthetic or natural because it improves the shelf-life of the products and protects us from harmful bacteria or microbes. 

The topic of preservatives is very controversial due to several popular ingredients being linked to causing hormonal issues. 

Lindsey Nelson explains what the all ingredients do that are in a bottle of shampoo.

More brands are becoming aware of their customers' concerns and are slowly removing harmful preservatives from their products.

Examples of preservatives are parabenssodium benzoatephenoxyethanolpotassium sorbateorganic acids, and benzyl alcohol.

Fragrances & coloring - Fragrances/perfumes are used simply to make the product smell good and look pretty.

Some of these ingredients, like panthenol or extracts from plants or fruits, have multiple purposes. 

Panthenol serves as a humectant by adding moisture and helping the hair retain it as well, but it also helps improve shine. 

Some thickeners, such as glycol distearate, also help add moisture.

Citric acid helps balance the hair's pH because it's acidic while also adding shine. 

Reading Between the Lines: Deciphering Ingredients Labels of Haircare Products

When you first look at the long list of ingredients in your shampoo or conditioner, you may need clarification because a lot of the words are outside your daily vocabulary.

But rest assured, just because we have a hard time pronouncing them does not mean they are harmful.

Label on the back of a bottle of shampoo

The label lists the ingredients in descending order from the greatest amount to the least amount.

So, for instance, in the photo above, AQUA is the ingredient that has the highest concentration and makes up most of the product, and FUMARIC ACID is the ingredient that has the least concentration.

If you are reading a label and an unfavorable ingredient is found, notice where it is located on the list, towards the top or the bottom.

If you are comparing a drugstore brand Vs. a professional brand, you will probably see the same ingredients on the labels.

But where the ingredients are located on the list may tell the difference between a $5-$10 bottle of shampoo compared to a $40 bottle.

Drugstore brands tend to use less quality ingredients in their products in order to keep product costs down.

Drugstore brands have come a long way, so claps to them for stepping up their game!

Now, that is not to say that all professional brands are perfect, either.

You just have to find the right ingredients and the right combination for your hair type, lifestyle, and budget.

Empowering Haircare Choices: The Importance of Ingredient Awareness

If this post has taught you anything, I hope you have learned the importance of knowing what ingredients you are putting on your hair.

Deciding on what product to buy can be overwhelming, but when you are equipped with the knowledge to make a good decision, you may feel better about your purchase.


Have we met?

Lindsey Nelson- Hair Stylist and Blogger located in Walker, Louisiana

My name is Lindsey Nelson, and I am a licensed Cosmetologist.

I have been in the hair industry for nearly 20 years, and I have a passion for educating my clients on the thing I know and love: hair!

I also have a blog for Cosmetologists

where we discuss all things beauty, and I help my readers grow their beauty businesses.

I work at J.Lene' Salon & Spa, located in Walker, Louisiana.

I am a wife and mom of 2, and I love coffee, Netflix documentaries, and True Crime!

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