Are Surfactants Bad for Your Skin? The Science Behind Cleansers

The same ingredients that make cleansing effective can also interact with the skin itself. This is why some cleansers leave the skin feeling comfortable and soft, while others can leave it feeling tight, dry or irritated.

So, are surfactants bad for your skin?

Not necessarily. The more useful question is which surfactants are used, how they are combined, and how the complete cleanser is formulated.

What are surfactants?

Surfactants are surface-active ingredients that help water interact with substances that would otherwise be difficult to remove with water alone.

This makes them extremely useful in cleansing products. They help loosen and disperse things such as oil, dirt and other residues so that they can be removed when the product is rinsed away.

Surfactants can be divided into several groups, including anionic, cationic, non-ionic and zwitterionic surfactants. Different types have different properties, which is why formulators can combine them to achieve a particular balance between cleansing power and mildness. (Cosmetic Formulation: Principles and Practice, 2019, Heather A. E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva and Kenneth A. Walters, eds.)

Why can cleansing make the skin feel dry?

The skin does not contain only dirt and excess oil.

Its surface also contains lipids and natural moisturizing components that contribute to the condition of the skin barrier.

A cleanser that removes too much can therefore affect more than the substances we actually want to wash away.

Research described in the Handbook of Cosmetic Science and Technology highlights the importance of selective cleansing: removing surface impurities while avoiding unnecessary removal of the lipids and natural moisturizing factors that are important for the skin barrier. (Handbook of Cosmetic Science and Technology, 2001, André O. Barel, Marc Paye and Howard I. Maibach, eds.)

This helps explain why two cleansers can both remove oil effectively but leave very different sensations afterwards.

Does more foam mean a better cleanser?

Not necessarily.

Foam is something consumers often associate with cleanliness, but the amount of foam does not tell you whether a cleanser is appropriately formulated for the skin.

What matters is how effectively the formulation removes unwanted substances without unnecessarily disturbing the skin.

A cleanser can therefore be effective without producing an enormous amount of foam.

This is particularly relevant when developing products for people who cleanse frequently or whose skin is more easily irritated.

What is the difference between different surfactants?

There is no single type of surfactant that is automatically best for every cleanser.

The Handbook of Cosmetic Science and Technology lists several types used in cleansing products, including soaps, sulfates, acylglutamates, acylglycinates, betaines and non-ionic surfactants. Their cleansing properties and effects on the skin can differ considerably. (Handbook of Cosmetic Science and Technology, 2001, André O. Barel, Marc Paye and Howard I. Maibach, eds.)

Some surfactants can be relatively harsh, particularly when used at inappropriate concentrations or in formulations that do not sufficiently account for skin compatibility.

Others can provide effective cleansing with a milder effect on the skin.

This is why a formulator will often use a combination of surfactants, rather than relying on a single ingredient.

What about “soap-free” cleansers?

The term “soap-free” can be confusing.

In cosmetic terminology, traditional soap refers to particular types of surfactants, while modern cleansers may use other surfactant systems instead.

So a cleanser labelled “soap-free” can still contain surfactants — and in fact, if it is designed to provide surfactant-based cleansing, that is exactly what you would expect.

The important question is therefore not simply whether a product contains “soap”.

It is what cleansing system has been used and how mild is the finished formulation?

(Cosmetic Formulation: Principles and Practice, 2019, Heather A. E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva and Kenneth A. Walters, eds.)

Can a cleanser actually support the skin?

Interestingly, yes.

Modern cleansing products do not necessarily have to be designed only around removing substances from the skin.

Some formulations include ingredients intended to help improve the condition of the skin after cleansing. These can include humectants such as glycerol, oils and certain lipid components.

The Cosmetic Formulation literature describes moisturising cleansers designed to deposit protective ingredients on the skin, helping reduce the drying effect associated with cleansing. (Cosmetic Formulation: Principles and Practice, 2019, Heather A. E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva and Kenneth A. Walters, eds.)

This is a good example of how the complete formulation matters more than any individual ingredient.

What makes a cleanser mild?

There is no single ingredient that automatically turns a cleanser into a mild product.

Mildness can depend on:

• the type of surfactants used;
• their concentration;
• the combination of surfactants;
• the product's pH;
• contact time with the skin;
• the presence of moisturising or protective ingredients;
• and the overall formulation.

The Handbook of Cosmetic Science and Technology describes combinations of surfactants as one way of reducing irritation while maintaining adequate cleansing performance. Amphoteric and non-ionic surfactants, for example, can be combined with anionic surfactants to improve the overall balance of the formulation. (Handbook of Cosmetic Science and Technology, 2001, André O. Barel, Marc Paye and Howard I. Maibach, eds.)

That balance is the real challenge.

A cleanser needs to remove enough unwanted material to do its job, but not so aggressively that it unnecessarily compromises the skin's protective function.