Inside the Bottle, Shampoo


 - By Kailey Bradt

Inside the Bottle, Shampoo

Before we get into Moondust Hair Wash and how it’s different, first we need to talk liquid shampoo.

Consider a recipe for baking a cake. Similarly, shampoo has a list of ingredients. And just like a cake, these general ingredients are what make a cake, well, a cake. Take flour, for example. There is all-purpose flour, whole-wheat flour, almond flour, etc. Pretty much any cake includes some type of flour, but the different types and amounts of this single ingredient result in a variety of different cakes. You get the idea. And so it is with shampoo.

Basically, shampoo comes down to a few general ingredients:

  • Water (in liquid shampoos)
  • Surfactants (Cleansing Agents)
  • Conditioners
  • Thickening Agents
  • Chelating Agents
  • Fragrance
  • Preservatives

Now you are probably wondering why the ingredient list on the back of your shampoo bottle is so long. In terms of the chemistry of shampoo, to get the modern, scientifically-advanced shampoo you are used to, you do need more than 6 ingredients. To keep it simple, here is the breakdown of the general ingredient list.


In a liquid shampoo, water is the primary ingredient. On average, water makes up 80% of the shampoo by weight. Water acts as a carrier solvent to deliver the other ingredients that have more necessary functions for your hair. Water can also be used to dilute harsh detergents, like sulfates, to reduce irritation when in use. With more recent raw material innovation, including the movement away from harsh detergents like sulfates, water is no longer serving that purpose. The ingredients we use today are milder, giving brands an opportunity to move away from water as a primary ingredient in shampoo. Like us at Susteau!


“Surfactant” is short for surface active agent. Surfactants decrease the interfacial tension between two physical states. In shampoo, surfactants allow for oil and water to get along with each other and form a uniform liquid called an emulsion. If oil and water did not get along, you would see two liquids sitting on top of each other, separated, in the bottle. When shampoo goes past its shelf life, you can see the oil and water phases start to separate. Surfactants can be responsible for a number of functions in shampoo - including wetting, emulsifying, foam boosting and anti-foaming, dispersing and cleansing.

In shampoo, the primary surfactant is categorized as a detergent. Detergents are responsible for shampoo’s primary function - cleansing!

Secondary surfactants are typically categorized as foaming agents, which boost the lather effect of your shampoo. Foam boosting agents aren’t just for show though! The foaming in your shampoo can help to lift the oil off of your hair and scalp to increase the cleaning effect. However, the ability of a shampoo to lather is not directly proportional to its effectiveness. A myth we will talk about in a later blog post.


Conditioners, well, condition the hair. Yes, it is that obvious. However, some conditioners are more effective for hair, whereas others are more effective for skin. In a shampoo, it’s important to have conditioners for hair and skin, because a well-conditioned scalp can help prevent dandruff and reduce irritation that may be associated with the surfactants in a shampoo. Conditioners are also responsible for properties of a shampoo like “smoothing” “shine” and “moisturizing.”

Thickening Agents

Thickening agents are self-explanatory in name, as well - they make your shampoo more manageable to pour out of the bottle by increasing the viscosity of your shampoo. A liquid that’s too runny will end up down the drain instead of in your hair!

Chelating Agents

Recently there has been an increase of chelating shampoos on the market, however this ingredient exists in almost all shampoos in some capacity. Chelating shampoos are simply shampoos with an increased level of the chelating agent. Chelating agents are responsible for removing build up in your hair by forming multiple bonds to a metal ion. Here is what that means. Where clarifying shampoos typically help to remove build-up in a physical way (i.e. salt), chelating agents remove build-up in a chemical way. For example, chelating agents can remove minerals from hard water that have accumulated in your hair. In a standard shampoo formulation, chelating agents allow shampoo to function as formulated in the presence of hard water. Chelating agents can be irritating and over-drying, so their percentage in shampoo is low, yet plays a necessary role. This is also why shampoo marketed for the chelating power should not be used regularly!


Fragrance. It’s arguably the first feature that is noticed when opening a bottle of shampoo. Fragrance gives a great sensorial effect- if you like the scent that is. Here is a fact you may not know, the term “fragrance” can be over 3100 different chemicals in the US as regulated by the Food & Drug Administration (FDA). Many brands are turning to fragrance transparency. 


Last but not least, we have preservatives. Preservatives do as they sound, they preserve the product in its manufactured state. One of the reasons products expire is because the preservative is no longer effective and microorganisms can grow - like mold, yeast, and / or bacteria. There has been a lot of controversy around certain preservatives, the most commonly known group being parabens. Parabens were a very popular preservative for a long time, because they are known as a broad spectrum preservative. Broad spectrum preservatives are effective against mold, yeast and bacteria. To replace parabens, multiple preservatives may need to be used.

Are preservatives necessary? In a liquid shampoo where 80% of the product is water, it is. Water sitting in a bottle over a period of a couple of years will grow some unwanted microorganisms. The use of preservatives should be based on risk and for a liquid shampoo, is necessary.

In Conclusion

So, that’s shampoo! We will touch more on certain general ingredient categories and specific ingredients in future posts.

Read the Details:

Parabens in Cosmetics
Surface Active Agents (Surfactants)
Then and Now: Shampoo Formulations through the Years


Image: 22 Tigers for Susteau