Surfactants, Emulsifiers and the Skin Barrier Part One
Jun 06, 2016
There is a lot of misinformation out on the internet surrounding emulsifiers and their use in cosmetics. There are companies who proudly state that they are emulsifier free and others who state that emulsifiers damage the skin barrier and can compound skin problems, hence why they don't use them. The implication being that any other company who uses emulsifiers has something inherently wrong with it and should be avoided....
I also have stressed out Estheticians emailing me so worried that they are causing harm with the products they are using because someone told them that emulsifiers were bad. This is indeed a REAL issue. Like any subject there is some truth to it and a lot of half truths and a lot of information completely not even told......and that is where I come in. I am going to cut through marketing hype and educate you to give you perspective.....
Given the wide depth of knowledge that is needed to be disseminated surrounding this topic, I have decided to break it up into smaller chunks so that everyone will understand it better. In this article I am to cover the classes of Surfactants.
This article on Emulsifiers is Part One of a series. The series of articles will cover:
- Different Classes of Surfactants.
- Surfactant interactions with the skin barrier.
- Emulsifiers and their effects.
- Emulsifier Types.
- Do you need moisturisers that contain DMS (Derma Membrane System) in order to have an intact skin barrier?
- What factors influence skin barrier homeostasis.
- The impact the amount of lipids in a formula has on the skin barrier
- Is there such a thing as Emulsifier Free?
Cleansing of the skin is a major component of modern hygiene. Cleansers come in many forms. Cleansers can consist of the following:
- Soap
- Moisturising soaps
- Cleansing Bars
- Gel Cleansers
- Micellar Water
- Cleansing Oils
- Cleansing Milks
The perfect cleanser is mild and does not irritate or damage the skin barrier. It increases hydration of the skin and leaves the skin feeling hydrated and softened. The purpose of cleansers is to emulsify dirt, oil and remove microorganisms on the skin surface.
Components in Skin Cleansers
Surfactants are a critical component of skin cleansing products. If you were to look at a typical cleanser or shampoo you would find that it consists of basically the following components:
- Water
- Surfactants (to emulsify the debris)
- Co-Surfactant
- Moisturizers (to hydrate the skin and maintain the skin barrier)
- Rheology modifiers, thickeners,
- Foam enhancers
- pH Adjusters
- Preservatives
- Fragrance
Let's look at a typical example of a cleanser:
This is Lancome Gel Radiance
Ingredients:
AQUA / WATER / EAU, PEG-120 METHYL GLUCOSE DIOLEATE, SODIUM LAUROYL OAT AMINO ACIDS, SODIUM COCOYL ISETHIONATE, DECYL GLUCOSIDE, POTASSIUM LAURATE, POTASSIUM MYRISTATE, ANANAS SATIVUS FRUIT EXTRACT / PINEAPPLE FRUIT EXTRACT, COCONUT ACID, SACCHARUM OFFICINARUM EXTRACT / SUGAR CANE EXTRACT / EXTRAIT DE CANNE A SUCRE, SODIUM ISETHIONATE, PHENOXYETHANOL, PEG-32, POLYSORBATE 20, LIMONENE, CAMELLIA SINENSIS LEAF EXTRACT, LINALOOL, BENZYL SALICYLATE, BENZYL ALCOHOL, PROPANEDIOL, PAPAIN, PYRUS MALUS EXTRACT / APPLE FRUIT EXTRACT, DISODIUM EDTA, METHYLPARABEN, CITRUS MEDICA LIMONUM PEEL EXTRACT / LEMON PEEL EXTRACT, HEXYL CINNAMAL, PARFUM / FRAGRANCE
So let's break these down into the different components of a cleanser:
Water :
Surfactants (to emulsify the debris) :
Co-Surfactant :
Moisturizers (to hydrate the skin and maintain the skin barrier):
Rheology modifiers, thickeners :
Foam enhancers :
pH Adjusters :
Preservatives :
Fragrance :
It is these different components above that have an enormous influence on how much or how little damage occurs from using cleansing products. The effect on the skin barrier is not just isolated to the surfactant chosen. It also has to do with the other ingredients contained in the formula. Hence why you see SLS (Sodium Lauryl Sulfate) being used in shampoos, alongside other actives such as proteins and humectants. The end result being a formula that does not necessarily dry or deplete the skin of lipids or denature proteins.
The word “Surfactant” is a contraction of the three words “Surface Active Agents.” Surfactants lower the surface tension between two liquids or between a liquid and a solid.
TYPES OF SURFACTANTS
With the growth in eco industries, there is now a wide selection of surfactants available to the cosmetic chemist. The type of surfactant used will depend on the intended end use of the product. For example is the product rinse off or meant to be left on the skin. The different end uses will determine which surfactants are suitable and cause the least irritation to the skin.
Surfactants can be classified 2 major classes:
- ionic surfactants
- nonionic surfactants.
Ionic surfactants can be further divided into anionic surfactants, cationic surfactants and amphoteric surfactant. [1,2].
Anionic surfactants
Anionic surfactants are the largest group of surfactants and the first to be developed. Anionic surfactants are those that have a negative charge on their polar head group. When dissolved in water the solution is either neutral or alkaline [3]. They include groups like carboxylic acids, sulfates, sulfonic acids, and phosphoric acid derivatives, of which the first three are most important in cosmetics. An example of a carboxylic acid anionic surfactants is stearic acid. It is often used for creating stick products. They are most useful for applications that require good cleansing and foam.
Sulfonic acid surfactants are generally more mild than sulfates. They include Taurates (derived from taurine), Isethionates (derived from isethionic acid), Olefin sulfonates, and Sulfosuccinates. The reason they are not used more often is that they are more expensive to produce and do not provide a significant enough benefit over Sulfates.
Examples of Anionic Surfactants include:
Stearic Acid
Sodium Stearate
Ammonium Lauryl Sulfate
Sodium Lauryl Sulfate
Sodium Laureth Sulfate
Sodium Lauryl Ether Sulfate (SLES)
Cationic surfactants
Cationic surfactants are positively charged [4]. They work best in an acidic medium and will precipitate (form crystals) in an alkaline medium. Cationic surfactants are often used in hair care due to it's substantivity (moisturised feeling). Cationic Surfactants also have antimicrobial properties.
The cationics include chemical classes such as Amines, Alkylimidazolines, Alkoxylated Amines, and Quaternized Ammonium Compounds (or Quats). Quaternium compounds are used in hair conditioners for their ability to be bond to the damaged (negative charge) part of the hair.
Anionic and Cationic surfactants can not be used together as they are incompatible.
Examples include:
Benzalkonium chloride
Cetylpyridinium chloride
Benzethonium chloride
Amphoteric (Zwitterionic) surfactants
Amphoteric surfactants which take with both positive and negative ions can be divided into imidazoline, betaine, lecithin, and amino acid-type type according to the anion type[1]. The toxicity of amphoteric surfactantsis very low. It is gentle to the skin, and has good biodegradability. Amphoteric surfactants have wide application in the personal protective equipment such as shampoo, shower gel, cosmetics, etc. and also can be used in industrial softeners and antistatic agents.
Amphoterics are primarily used in cosmetics as secondary surfactants. They can help boost foam, improve conditioning and even reduce irritation. They are also used for baby shampoos and other cleansing products that require mildness. The drawbacks are that they do not have good cleansing properties and don’t function well as emulsifiers.
Examples include:
Cocamidopropyl betaine
Sodium Lauriminodipropionate
Disodium Lauroamphodiacetate.
Non-ionic surfactants
Nonionic surfactants have no charge on them. [1]. Most non-ionic surfactants are in liquid form and they do not interact with the proteins of the skin. They are incredibly gentle and cause minimal irritation to the skin. Non-ionic surfactants are used often as emulsifiers and conditioning ingredients. The newer sugar based surfactants are non-ionic in class.
Examples include:
Cetyl alcohol
Stearyl alcohol
Decyl Glucoside
Polymeric surfactants
Polymeric surfactants have a large molecular mass. According to the natural source, they can be divided into natural type, modified natural material and composing categories[1]. Polymer surfactants can be used as thickener, gelling agent, fluidity-improving agent, emulsifier, dispersing agent and antistatic agent. It has become an important member of the surfactants family.
Examples include:
Hydroxypropylmethylcellulose
Carbomer
Acrylates/C10-30 Alkyl Acrylate Cross-polymer
Surfactants are widely used and are an essential component of skin cleansing systems. With the introduction of new surfactants it is indeed possible to formulate skin cleansers that respect the skin barrier. In Part Two of this series we will discuss exactly how surfactants can interact with the skin barrier, the negative consequences of surfactant use. In Part Three we will examine how all of this can be avoided or mitigated by correct use of ingredients when a chemist formulates.
About the Author
Jacine Greenwood is an internationally recognised educator who is known within the industry for her up to date knowledge and her ability to deliver training in an easy to understand method.
Jacine holds 4 Diplomas and a Bachelor of Nursing and her knowledge is well respected by her peers. With over 21 years experience in the industry and a background of cosmetic formulation, Jacine has an immense knowledge of current trends in research and new developments in the industry.
Jacine has been continually educating herself in all aspects of skin function and cosmetic chemistry for the past 21 years. Jacine’s knowledge is current and has a vast knowledge of the active ingredients that are being released onto the market.
References:
SR Wang; XG Li; DZ Liu,Surfactant chemistry, Beijing: Chemical Industry Press,2005, 5-10.
TS Zhang,Surfactant application technology, Beijing: Chemical Industry Press, 2001, 2-7.
TM Schmitt, Analysis of Surfactants, 2nd Edition, M. Dekker Press, New York, 2001.
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