The surfactant guide - Part 1

So, today I would like to write about a topic that is very close to my heart. Besides UV protection, of course! :) 

It's about the cleanser of the skin. Or rather, the right cleanser and what you should bear in mind. So that your skin really gets the best possible care that you can give it. So it's all about surfactants, their use as washing-active substances and I'll also take a brief look at their side business: Surfactants as emulsifiers. 

Because many of you may be wondering what surfactants really are, what they do to the skin and whether surfactants are perhaps even dangerous? 

That's why I'm giving you 6 facts about surfactants that you should know so that you can better understand and choose your cleaning products in the future! 3 of them come in part 1, let's go! 

#1 Surfactants are amphiphilic substances 

Fig. 1 

"Amphiwas" you ask? Amphiphilic means that the molecule has a part - in this case we call it the "head" - that feels super comfortable in water-like substances, or water. The other part of the molecule, on the other hand, in this case the "rest", loves fats and oily substances. Depending on the charge of the head and the greater the difference between the head and the rest, the more polar and active the surfactant is. 

It also owes its areas of application and mode of action to this property. I found a great comparison in Heinz Knieriemen's critical guide to cosmetic ingredients. Knieriemen describes surfactants as the brownies of cosmetics. (1) In my opinion, this is an absolutely appropriate term that does justice to the many possible applications of surfactants. You can find surfactants in soaps, shampoos and cleansers for the skin, but also in household products. And we use them when mixing creams. 

# 2 Surfactants Treat as washing substances and emulsifiers

Fig. 2 

Because surfactants (from the Latin "tensus" = tense -> reduce surface tension) like both fat and water, they can combine these two substances, which actually repel each other. This always makes me think of salad dressing. If you shake or stir the dressing and leave it to stand for a while, the oil will always settle. To achieve a uniform liquid, you would need a surfactant/emulsifier that reduces the surface or surface tension of the substances. But let's leave that out of the salad. :) 

An emulsifier is indispensable in creams. For example, we need a substance that combines plant-based oils, such as our Argan Oil, with water-soluble active ingredients such as hyaluronic acid. Tadaa - who would have thought it, the hard-working surfactants take over. 

They stick their head into the hyaluronic acid, so to speak, and the rest grabs the Argan Oil, encloses it in small globules (see Fig. 2) and distributes it throughout the entire "mass". Incidentally, these are the so-called micelles. More on this further down in the article. 

This is how a cream is created. There are oil-in-water emulsifiers and also water-in-oil emulsifiers. If you like, I can also write a separate article about this. Let me know what interests you! 

Yes, and because surfactants are so good at mixing, they are also considered excellent cleansing agents. They help the water to remove grease-soluble dirt and make-up from our faces, so to speak. Of course, they also do this in the kitchen, the washing machine and so on. Just like Argan Oil, in this case they trap dirt particles and distribute them in the washing water. Pretty cool in my opinion.    

# 3 Surfactants are distinguished primarily by their water-loving "head" 

Fig. 3 

As you can see in my Fig. 3, some of the hydrophilic ends carry electrical charges and some do not. These charges determine how well the surfactant dissolves in water, which pH-value the surfactant brings with it and therefore also its mode of action. In addition, this charge also determines how strong and therefore how aggressive a surfactant is for our skin and the environment!

There are 

• anionic surfactants 
• Cationic surfactants 
• amphoteric surfactants
• Neutral/non-ionic surfactants 

So that I don't have to beat about the bush so much, I have created a few diagrams and drawings for you. I hope you can understand them and they help you to better understand the characteristics of our little brownies.

Anionic surfactants 

Fig. 3.1 

The negatively charged surfactants have the highest cleaning power and are found in many rather foaming detergents and gels. A very common representative here is sodium laureth sulphate! In Fig. 3.1 you can see how the name is made up.

Sulphates are among the most aggressive surfactants. This is because they do not stop at your skin oils and therefore attack your protective acid mantle. They open the door to germs and unwanted foreign bodies. As a result, they are suspected of causing allergies, dry skin, brittle hair and a flaky scalp. (3)

NOTE: You can usually recognize anionic surfactants by the term "sodium" (the counterion for the negative charge) and "sulphate" surfactants should be avoided. 

However, there are of course also non-ionic surfactants, such as disodium cocoyl glutamate, which is somewhat milder and therefore better tolerated. It always depends on what cleaning power you want from a product. The important thing is that you are aware of what you are dealing with. The decision is ultimately up to you! 

What I ask myself at this point, however, is whether our skin needs such a strong cleanser? After all, healthy skin does have good self-regulation. It is an autonomous organ. We want to do everything we can to ensure that the skin can carry out its tasks and, above all, its abilities unhindered. 

Of course, external influences change and our lifestyle often leaves its mark. This makes it all the more important to avoid irritating substances as much as possible and to take skin health seriously. 

Speaking of health, the health of our environment also plays a major role, especially in connection with the topic of surfactants. More on this later.  

The soap

Anionic surfactants also include normal soap surfactants. They are formed when fats, such as coconut oil, are broken down using an alkaline solution. This process, also known as saponification, produces a potassium or sodium salt of the original fatty acid. 

Soaps are not ideal for our skin. This is because they cause the skin to swell and attack the protective acid mantle. This is also due to the rather high pH-value of 7-8. (3)

However, a high washing power can be desirable, especially when washing hands, which is why the tried and tested soap is often used. Apart from that, it is also readily biodegradable.  

Cationic surfactants 

Fig. 3.2

Ammonium compounds are preferably used here in order to maintain the positive charge of the cationic surfactants. The counter ion is often the chloride anion. Since cationic surfactants tend not to be used as washing raw materials, but rather in hair shampoos and conditioners to ensure that the hair does not fly after washing, I am neglecting them a little here. 

Cetrimonium Chloride would be an example INCI. (2)

Neutral/non-ionic surfactants

Fig. 3.3

As their name suggests, neutral surfactants carry no charge. They are therefore also very mild and skin-friendly. But they also hardly foam at all. They include a range of very chemical-sounding surfactants.

Fatty acid ethanolamides, fatty alcohol ethoxylates, macrogol fatty acid esters (PEG) and alkyl polyglycosides.

The alkyl polyglycosides are my favorites here. They are also called sugar surfactants as their hydrophilic head consists of a sugar molecule. They have virtually no effect on the skin barrier and also greatly reduce the irritation potential of other surfactants. They improve the dry combability of the hair, its bounce and tensile strength. Top surfactants in other words!

You can often recognize them by the word stem "glucoside" or "sucrose". 

Amphoteric surfactants 

Fig. 3.4 

This surfactant group combines the positive properties of anionic and neutral surfactants. They are mild, but still have good cleaning power and even a very acceptable foaming performance! They are also readily biodegradable. (2) 

You can recognize them by the word stem "betaine" and "-ampho-"! 

Betaines owe their name to betaine. A substance that is very similar in structure and comes from the sugar beet (Beta vulgaris). They are often used in combination with anionic surfactants in order to reduce their irritation potential while maintaining good cleansing power.

Now you're at least well prepared when it comes to the basics of surfactants. You can find out more about what the micelle is all about and how to gently but effectively cleanse your skin in the next blog post! 

Take time for yourself & be good to yourself! 

Your Leonie 

Sources

1. Cosmetic ingredients from A to Z, Heinz Knieriemen, 6th edition, 2005, AT Verlag Baden and Munich
2. Body care science and cosmetics, Sabine Ellsässer, 2nd edition 
3. Guide to the world of cosmetics, Esther Witte, 2nd edition, 2019