An example shower gel formulation*:
Chemical name | CAS No | Amount, % | Purpose |
Water | 7732-18-5 | 80.35617 | Carrier, solvent |
Sodium laureth sulfate | 1335-72-4 | 10 | Surfactant |
Cocamidopropyl betaine | 61789-40-0 | 3 | Surfactant |
Sodium laureth-6 carboxylate | 33939-64-9 | 2 | Foam booster |
Cocamide methyl MEA | 866889-75-0 | 2 | Thickener |
Sodium chloride | 7647-14-5 | 1.5 | Thickener |
Fragrance | Mixture | 0.5 | Self explanatory |
Polyamino sugar condensate | 120022-92-6 | 0.3 | Moisturizer |
DMDM hydantoin | 6440-58-0 | 0.165 | Preservative |
Disodium EDTA | 139-33-3 | 0.1 | Chelating agent |
Citric acid | 77-92-9 | 0.06 | pH adjuster |
Methylchloroisothiazolinone | 26172-55-4 | 0.0009 | Preservative |
Methylisothiazolinone | 2682-20-4 | 0.0003 | Preservative |
Magnesium chloride | 7786-30-3 | 0.0008 | Inert preservative component |
Magnesium nitrate | 10377-60-3 | 0.0168 | Inert preservative component |
CI 42090 | 3844-45-9 | 0.00002 | Dye |
CI 16185 | 915-67-3 | 0.00001 | Dye |
The shampoo formulation can be structurally broken down into the following categories:
Let’s talk about every component in the formulation:
Water:
Not much to say — it acts as a carrier for other components.
Sodium Laureth Sulfate (SLES):
One of the cheapest surfactants available on the market. It provides excellent foaming, but it is a sulfate. Some people avoid it because it’s an ethoxylated surfactant, which may contain traces of 1,4-dioxane. Despite some controversy, it is widely used. SLES is sold in diluted (27% active) and concentrated (70% active) versions. A 10% concentration in a recipe refers to the pure substance, which translates to approximately 37% of the 27% active version or around 14.28% of the 70% active version.
Cocamidopropyl Betaine (CAPB):
An amphoteric surfactant often used in combination with SLES. It is cost-effective and helps reduce the irritation potential of harsh anionic surfactants. The SLES and CAPB blend forms the backbone of most economical personal care formulations. CAPB is typically supplied at 30% or 40% active concentrations. The concentration listed in the recipe refers to the pure substance.
Sodium Laureth-6 Carboxylate:
A foam booster and very mild surfactant that enhances the overall mildness of the product.
Cocamide Methyl MEA:
A thickener that increases the product’s viscosity. It can be used interchangeably with for example PEG-4 Rapeseedamide at a 1:1 ratio.
Sodium Chloride:
Also acts as a thickener in SLES+CAPB formulations. It can be used alone as a thickener, but this requires a significantly higher concentration (around 5–6%), which is not recommended as high salt levels in shampoo may cause dryness and irritation.
Polyamino Sugar Condensate:
A fancy moisturizer made from sugars and amino acids. Alternatives include sodium PCA, sodium lactate, D-panthenol, and amino acid blend.
DMDM Hydantoin:
A preservative that slowly releases formaldehyde — a toxic compound — to inhibit microbial growth and extend shelf life. It may cause allergic reactions in some individuals.
Disodium EDTA:
One of the best chelating agents, used to bind and neutralize metal ions. It’s important to note that this material is not biodegradable and poses a considerable environmental impact.
Citric Acid:
Primarily used to adjust pH. Most shampoos have a pH around 5.5.
Methylchloroisothiazolinone, Methylisothiazolinone, Magnesium Chloride, Magnesium Nitrate:
These components in water form the Kathon CG preservative system. This blend likely enhances the preservative activity of DMDM Hydantoin.
CI 42090, CI 16185:
Dyes that provide no functional benefit beyond improving the product’s visual appearance.
*https://hdsupplysolutions.com/wcsstore/ExtendedSitesCatalogAssetStore/product/fm/additional/28/287493_MSDS-PDF.pdf