Why cosmetic ingredients with the same name aren’t always the same

When you learn chemistry in school, they teach you the molecular structure of materials and the chemical and physical characteristics of the compound. It’s easy to get the impression that the world is filled with these discrete materials that behave in predictable ways.

That’s why I found it strange when I started in the cosmetic industry that many cosmetic ingredients which share the same name, were actually not chemically identical. And it’s this lack of being identical that is the reason you can’t simply switch one supply of a material out for another without doing appropriate testing.

But why are materials with the same name different?  There are a few reasons.

Composite materials

The majority of raw materials used in making cosmetic formulas are not pure ingredients. They are often mixtures of a number of ingredients. For example, Glyceryl Stearate is a common cosmetic emulsifier. You might think when you purchase glyceryl stearate from a raw materials supplier you are getting a molecule that looks like this.

But the reality is that when you buy glyceryl stearate, the composition of what you are buying is usually only just “mostly” glyceryl stearate. The ingredient is usually composed of a number of different materials including Glycerin, Glyceryl Distearate, & Glyceryl Tristearate. There might also be Stearic Acid, Palmitic Acid, and a wide range of other fatty acid esters that aren’t glyceryl stearate.

This is because the raw material supplier does not have 100% control over the chemical reactions that create Glyceryl Stearate. The chemical reaction can lead to various final compounds and can also leave unreacted starting materials. That’s why there are specifications.

Specification differences

A company like Oleochemicals offers at least four different types of ingredients that all have the name Glyceryl Stearate. But they differ in how much glyceryl stearate and other ingredients are present. Their Imwitor 491 is 90% glyceryl stearate while their Imwitor 900 contains between 40 - 55% glyceryl stearate. Both of them have the INCI name Glyceryl Stearate.

When you compare the Glyceryl Stearate between companies you’ll find that they also have different specifications which can lead to a different composition of the ingredient you’re buying. This is why it is so important for your company to have its own internal specification for every raw material that you buy.

Synthesis method

Another thing that makes ingredients that otherwise have the same name different is the way in which they are produced. Chemical suppliers may have different methods by which they synthesize whatever raw material you are making. These different chemical synthesis pathways may lead to the same primary ingredient, but could have vastly different residual ingredients. For example, consider an ingredient like Sodium Lauryl Sulfate.

This useful detergent is synthesized by reacting lauryl alcohol with sulfur trioxide gas, oleum (sulfur trioxide solution), or chlorosulfuric acid. This produces hydrogen lauryl sulfate which is then neutralized with something like sodium hydroxide or sodium carbonate to produce Sodium Lauryl Sulfate.

As you can imagine, whether you use sodium carbonate, sodium hydroxide, sulfur trioxide or chlorosulfuric acid, you’ll have a slightly different end product. The majority of it will be SLS, but the complete material may be slightly different.

Different starting materials

Related to the different synthesis method is the fact that you can produce the same material from different starting feedstocks. Sticking with Sodium Lauryl Sulfate, you can produce it by starting with pure Lauryl Alcohol (that you might have gotten from petroleum sources) or you can start with an oil like Coconut oil or Palm Kernel oil.  These plant sources must be first hydrolyzed then hydrogenated to make the fatty alcohols.  What you are left with is a blend of fatty alcohols, the majority of which are Lauryl Alcohol. But this might lead to Cetyl Alcohol, Myristyl Alcohol, and Stearyl Alcohol too. So your end material which is called Sodium Lauryl Sulfate may actually have a large amount of Sodium Cetyl Sulfate, Sodium Myristyl Sulfate and Sodium Stearyl Sulfate.

Post Manufacturing changes

Another thing that can make ingredients with the same name different are some post-production things that are done. In the manufacture of materials there are often quirks that each manufacturing plant has that have to be adjusted for.

For example, some raw material suppliers put preservatives in their ingredients to kill off any in-house bacteria that could possibly grow in the material while it’s being stored. There might also be things done to the ingredient to reduce the color if it became too yellow during production. These changes might not even be noticeable on your specification sheet but they can lead to differences in formula stability or the way your end product performs.

Dealing with raw material variations

Now that you know how raw materials can be different, it’s important to keep in mind when you are formulating. During the development phase, always use the same supplier for any specific raw material. Once you have your working prototype then you can see if the formula still works using a material from some other supplier.

And when you have to find a second source for any material (and you should always have a second source for all materials) be sure to conduct tests like stability testing and performance testing on every affected formula.

Remember, just because an ingredient has the same INCI name that doesn’t mean it is the same ingredient.  Test to make sure!