Shampoo Surfactants: What Are They?

“Surfactants” or “Surface Active Agents” are chemical compounds that help clean during washing (laundry, hair, skin, etc.). Since water is a polar universal solvent that dissolves most dirt, debris, and materials, surfactants help water to better penetrate and remove them.

Despite water being able to dissolve most substances, it faces some difficulty interacting with substrate materials such as hair, skin, and fabric due to a dynamic force called surface tension, which resists the penetration of water molecules.

Surfactants can decrease the water’s surface tension and improve its cleaning capabilities. They also act as emulsifiers that can remove grease and debris, which can then be rinsed off with water. ^1-3

Shampoo needs surfactants to clean hair effectively and remove sebum, oil, debris, and product build-up over the hair shaft. Without surfactants, shampoo would not have this ability.

Frequently Used Shampoo Surfactants

Shampoo usually contains either anionic or non-ionic surfactants. The shampoo is made up of a combination of two to three surfactants to achieve the desired cleansing, foaming, and conditioning properties, as well as aesthetic features.

Anionic surfactants, like Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES), are the most common ones used in shampoos. They have a part in their structure that carries a negative charge.

Because of this negative charge, anionic surfactants are really good at cleaning our hair, making lots of lather (foam), and they are affordable too. ^4-5

Here is a list of the commonly used surfactants:

• Sodium Lauryl Sulfate (SLS, Anionic)
• Sodium Laureth Sulfate (SLES, Anionic)
• Sodium Coco-Sulfate (Anionic)
• Ammonium Lauryl Sulfate (Anionic)
• Ammonium Laureth Sulfate (Anionic)
• Sodium Lauroyl Sulfoacetate (Anionic)
• Sodium Lauroyl Sarcosinate (Anionic)
• Sodium Lauroyl Glutamate (Anionic)

Organic molecules known as non-ionic surfactants have no charge density and produce moderate to low foam. They possess excellent cleansing abilities and are particularly beneficial for the skin as they are less likely to cause irritation compared to anionic surfactants.⁶

This makes them perfect for products made for sensitive scalp consumers and kids. Some examples of non-ionic surfactants include:

• Coco Glucoside
• Decyl Glucoside
• Lauryl Glucoside

In addition to the two previously mentioned groups, another type of surfactant known as amphoteric surfactant is commonly used in shampoo. These surfactants are great at increasing the amount of foam in the shampoo and help to maintain the viscosity of the liquid formulation.

Some examples are:

• Cocoamidopropyl Betaine (CAPB)
• Coco Betaine
• Cocoamphoacetate Sodium

Shampoo Formulation: Surfactants & Co-Surfactants

Typically, a shampoo’s formula includes two to three types of surfactants. The main surfactant is used in high quantities and serves as the foundation of the product, providing primary cleansing and foaming.

Additional surfactants, called co-surfactants, are added in smaller amounts to improve the primary surfactant’s cleansing and foaming abilities and enhance the shampoo’s overall performance.

A co-surfactant to the main surfactant lowers the critical micelle concentration and improves the product’s ability to clean and create foam.

Together, these surfactants can effectively remove oil, fatty materials, debris, and particulates from hair. As a team, they work together to provide the desired cleansing and aesthetic qualities.

In the above list of surfactants, SLES is used as the main surfactant, but it may not be enough to give a shampoo the desired cleansing, foaming, and foam stability.

To enhance these properties, a co-surfactant called Cocamidopropyl betaine (CAPB) is added, which greatly improves the shampoo’s cleansing, flash foam generation, and foam stability.

Vilifying a Single Surfactant 

Shampoo formulations usually contain a blend of two to maybe even different types of surfactants in a specific order and ratio. It is very rare for a shampoo to have just one surfactant.

Moreover, the combination of surfactants from different chemical groups affects the compatibility of the formula with the skin and reduces the likelihood of irritation.

With that said, it is important to note that blaming a single surfactant for any negative consequences or outcomes is not accurate. The quality of a product should not be determined by just one or two ingredients, but rather by the overall formulation.

Lately, there has been a tendency to unfairly criticize a single ingredient, which is not a scientific approach. People have been criticizing one ingredient without considering the science.

One example is the debate surrounding the sulfate surfactants SLES or SLS and their potential to cause irritation. The fact is, no one uses these chemicals directly on their hair. They are always part of a formulation and are mixed with other surfactants and ingredients.

Even though SLS and SLES are harsh and have relatively high irritation potential, the presence of other ingredients in the formulation (co-surfactants, or conditioning ingredients) can mitigate their severity and can still make a skin-friendly product.

There are many shampoos and facial cleansers on the market that contain SLS & SLES and have a mild, gentle formula. Additionally, SLS is commonly present in oral hygiene products. ⁷

Hence, it’s not appropriate to single out one ingredient. Instead, it’s always a good idea to experiment and find the products that suit your hair best.

As I always say, let your hair be your guide!

Summary

Surfactants are the backbone of hair shampoo. They help to clean, create lather, and remove dirt from hair. A typical shampoo usually contains a combination of anionic, non-ionic, and amphoteric surfactants that are mixed in a specific proportion.

The overall effectiveness of a shampoo doesn’t depend on just one single surfactant. It is the combination of all ingredients that makes a shampoo work. Therefore, singling out and demonizing one particular ingredient is not a scientific approach.

The best approach to figuring out what products work for your hair is through trial and error. Choose a shampoo with ingredients that best suit your needs and let your hair be the judge!

I hope I have cleared up some of the confusion around shampoo surfactants. As always, if you have any questions, just ask away in the comments section!