Beyond the Buzzwords: A Cosmetic Chemist’s Guide to Shampoo Ingredients

I recently moved, and as I was unpacking, I found my first formulation book gifted to me by a colleague in my early days as a bench chemist. Titled, “New Cosmetic Formulary” and dating back to 1970, the book helps set up a framework for common cosmetic categories and serves as a useful guide for product formulation. One can appreciate the simplicity of the recipes, with most formulas under 10 ingredients, focusing on ingredient functionality above all else.

Today, it’s common to see ingredient labels expanding over 50+ ingredients, many of which may not be necessary to product functionality. In an effort to promote a less is more approach to product use, let’s learn about the key ingredients in a shampoo, how they work, and when you need them. Then we’ll look at how this framework inspired our shampoo bar.

Solvent: in a liquid shampoo, we dilute surfactants (cleansing ingredients) in water for convenience and ease of use. The water portion makes up about 80% of the final formula.

Primary Surfactant: usually led with an anionic surfactant. Examples include sodium lauryl or laureth sulfate, ammonium lauryl or laureth sulfate, sodium cocoyl isethionate, sodium methyl cocoyl taurate. As anionic surfactants are very effective at cleansing, they can be perceived as “harsh” on their own so these will typically be paired with milder surfactants for a gentler cleanse. Common examples fall into the glucosides and glutamates categories.

Secondary Surfactant: to modify the foam quality (the lasting lathering feeling, foam tightness, creaminess,) liquid shampoos will often contain a secondary surfactant that’s usually amphoteric. These don’t quite cleanse as well as their anionic counterparts, yet do improve the liquid shampoo sensorial experience. Certain amphoteric surfactants can also improve product viscosity or thickness. Examples include cocamidopropyl betaine or cocamidopropyl hydroxysultaine.

Conditioning Agent: unless it’s a true clarifying shampoo, most shampoos contain a conditioning element to minimize washed hair from feeling dry or stripped. These are typically cationic ingredients, meaning they are positively charged and are attracted to negatively charged hair strands, even when shampoo is rinsed off. Examples include guar hydroxypropyltrimonium chloride or polyquaternium-(insert number here.) Some shampoos may use a small amount of silicones or oils that can have some substantivity and minimize the perceived dryness that’s associated with a thorough cleanse. 

Thickener: in the early days of liquid based shampoo, the user would mix hot water with powdered cleansing ingredients and would wash hair with a watery, tonic-like solution. Modern liquid shampoos have an element of viscosity (gel-like thickness) that may create a pleasant sensorial experience. This could be achieved with the correct ratio of surfactants and salt. However, depending on the surfactant blend, sometimes an additional thickening polymer may be included to keep a shampoo from feeling runny. On a label, examples could look like acrylates copolymer, carbomer or guar gum.

Fragrance: a sensorial improvement as shampoo ingredients do have a base odor.

Chelator: have you noticed your shampoo foaming less where there’s hard water? A chelator binds to metals that may be in water, to keep them from interfering with product performance. Examples include Disodium EDTA, Tetrasodium EDTA, Sodium Phytate, Sodium Gluconate.

Preservative: if something is water-based, it needs a preservative. Examples include phenoxyethanol, benzyl alcohol, sodium benzoate, potassium sorbate, parabens and methylisothiazolinone. 

pH adjuster: hair likes an acidic environment, and certain ingredients may require certain pH conditions for optimal performance. 

Opacifiers: while not required, sometimes these ingredients will be added to create a luxurious and pearlescent appearance. Or, if some of the ingredients create turbidity or haziness in a formula, opacifiers are used to create a uniform consistency. Examples include Glycol Distearate, or sometimes glyceryl stearate. Clear shampoos don’t use these.

Color: also not required but can add to a marketing story

The Anatomy of our Hyaluronic+ Solid Shampoo Bar 

Due to the concentrated nature of our shampoo bar formula, we eliminated the need for several ingredient types that would otherwise be critical to a traditional liquid shampoo, including texture modifiers, foam boosters, salt, etc.  All ingredients serve a functional purpose. Surfactants: Sodium Cocoyl Isethionate, Sodium Lauroyl Glutamate

Conditioning: Guar Hydroxypropyltrimonium Chloride, Hydroxypropyltrimonium Hyaluronate (also known as Cationic Hyaluronic Acid,) Meadowfoam Oil 

Fragrance: the base smells like crayons (not in a good way) if we don’t use fragrance 

Chelator: Sodium Gluconate 

Opacifier/Structuring: Stearic Acid & Kaolin 

pH adjuster: Fumaric Acid 

I formulated the shampoo bar to sit at a pH of about 5.5, which is in the optimal range for shampoo. The end result is a simple and balanced formula that richly lathers, thoroughly cleanses and rinses clean without a residue. As an added benefit, the bar format of this shampoo eliminates the need for bottled packaging waste.