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How Soap and Cleansers Work

woman washing her face

If you use nothing else on your skin, I know you do use a cleanser! There is a huge array of products out on the market, with many different price points, different additives and different formulations. Here I’ll be reviewing how soap and cleansers work to clean your skin. Pretty much all how soap and cleansers work this way, whether it is Dawn Dish Soap or a super expensive facial cleanser from Chanel. Quick, read the epidermis post if you haven’t yet (or re-read it if you have, I added a few things) before we start!

how surfactants work in soap

How Soap Works

All soap and cleansers work the same way, whether a $1 bar of soap or a $100 bottle of La Mer cleanser. Really! In order to both get rid of oils, sweat and dirt on the skin while making the whole thing water soluble, surfactants are used. Basically, look at the left side of the picture above. This is the basic soap molecule. There is a long chain of non-polar (neutral) atoms (that part that looks like a tail) and this part is attracted to the dirt, oil, etc. The other end (the polar, or charged end) is attracted to water. So, lots of little soap molecules will surround the piece of dirt, oil or whatever; see the right side of the picture. Note how they surround the offensive bit with their non-polar end, and the polar (water attracting) end is out into the water, allowing the whole thing to be water soluble.

Note that not all cleansers are technically “soap.” There are soaps and detergents, the difference is the way in which they are made, in addition to their pH. Soaps tend to be more alkaline, and as such may result in more drying and irritation of the skin. Both work through the surfactant mechanism I just described, and there are different fats and additives that compose the rest of the cleaners.

The whole thing sounds pretty simple, doesn’t it? Well, there are definite downsides to this whole process.

1. Redness and Irritation: The soap molecules may surround and damage the Keratin within the skin. This allows the Keratin to swell and become overhydrated, damaging the skin and it’s barrier function. In turn, this allows the soap to penetrate more deeply into the skin, where they interact with nerve endings and are attacked by the body’s immune system, resulting in irritation, redness and itching.
2. Dryness: The soap molecules may remove some of the lipid between the cells of the Cornified Layer, and may also remove some of the moisturizing molecules within the cells of this layer as well.
3. Tightness after Washing

The extent to which a soap is irritating depends upon several thing- the potency of the surfactant, the pH of the soap (higher pH=more basic/alkaline=more irritating, irritating soaps will be in the range of 9.5-11), and rinsability. All of these effects are minimized by adding moisture through depositing lipids and humectants (things that attract moisture) into the skin. As well, artificially created surfactants (also called syndets) are less harsh on the skin than more naturally created surfactants.

Types of Cleansers

There are many fomulations of cleansers out of the market today, and often the only way to discover what type of cleanser you have is to check the label!

Most soaps can be easily divided in terms of their composition, I find this the easiest way to think of them.
1. Soap: Old fashioned soap, pH is usually 9-10
2. Combars: Combines soap with “surface active agents” with a pH 9-10
3. Syndet: Synthetic detergents rather than than mostly soap surfactants, they usually are<10% soap, and have a pH of 5-5.5 which means they are often more gentle on your skin.

Soaps are also commonly divided by how they are made, especially those that are in bars. I’m not going into the whole process or explanation, but you can read a pretty decent explanation of it here on Wikipedia.

Considerations for Certain Forms of Cleansers

1. Liquid: When liquid soaps first came out, they were quite the revolution in the cleansing industry. Their formulas allow milder surfactants and more (and better quality) moisturizers to be used.
–Emollient-Rich vs. Humectant-Rich: Both are forms of moisturizers, however humectants simply attract moisture to the epidermis, and are easily washed off of the skin. Emollients help to fill in the spaces between the corneocytes in the cornified layer, and as they are not water soluble, they are not easily washed away. Emollient rich body washes are made by Dove and Olay.
2. Bar: Bar soaps are typically more aggressive in terms of their surfactants. This means that not only will they do a better job of removing soap and oils, they also will be more likely to irritate and dry out the skin.
3. Lipid free cleansers: A liquid cleanser that cleans without fats, it removes dirt and makeup easily and leaves behind a thin film. Often used by those with sensitive skin.
Usually contains: water, glycerin, cetyl alcohol, stearyl alcohol, sodium laurel sulfate (a detergent), and propylene glycol (can cause stinting).
4. Cleansing Creams/Cold Creams: They seem old fashioned I know, but they are pretty great for dry skin. Usually contain water, mineral oil, petrolatum, and waxes, they use a borax derived detergent (decahydrate of sodium tetraborate)
5. Body Washes: Depends upon a little plastic poof to add water and air to disperse the product (you know the one I mean, it’s hanging in your shower right now), they are made of synthetic detergents (therefore less harsh on the skin) and they can have high amounts of petrolatum for hydration (Oil of Olay’s body wash has 17%, I heard from a dermatologist that this is the highest % on the market).
6. Low-foaming Washes: Often used to wash the face, often they have little to no surfactant, but do not contain moisturizers such as humectants or emollients. Cetaphil fits into this category.

Common Cleanser Ingredients

Pretty much all surfactants are made from an oil/fat which reacts with a base, producing the surfactant molecules you saw in the pic above. The length of the carbon chain “tail” depends upon which oil you started with, for example those with 10-14 carbons in the chain are more aggressive and more irritating (these are mostly derived from coco oil).

How to read an Ingredients list at The Beauty Brains

SurfactantsNatural soapsynthetic surfactants
Preservative/Antioxidants(BHT) butyl hydroxy toluene2-t-butylbenzene-1
Detergentssodium cocoate
sodium tallowate
sodium palm kernelate
sodium stearate
sodium palmitate
triethanolamine stearate
sodium cocoyl isethionate
sodium isethionate
sodium dodecyl benzene sulfonate
sodium cocoglyceryl ether sulfonate
sodium laureth sulfate- a harsher surfactant
cocoamido propyl betaine
lauric acid diethenolamine (lauramide DEA),
sodium cocoyl isethionate
disodium laureth sulfosuccinate
Decahydrate of sodium tetraborate
Ammonium Lauryl (or Laureth) Sulfate – a milder surfactant
Preservative/Sequestering agent (keep hard minerals in the water)(EDTA) ethylene diamine tetraacetic acid
(EHDP) hydroxyethane diphosphonic acid, also known as editronic acid
Complex phosphates and sodium citrate
Whitening agentTitanium dioxide
Processing aidsSalt
FillersStarch, clays, salts, etc.
Lather BoostersCo-surfactants (e.g., SLES and betaine)sodium carboxymethylcellulose
Antibacterial AgentsBenzoyl Peroxide
Resorcinol antibacterials
–triclocarban- attacks gram + bacteria
–triclosan- attacks gram + and – bacteria
Moisturizers/Skin Feel AgentsPolyols
Humectant-Attract water from the dermis into the epidermis, and from the air in humidity >70%Acetamide MEA
Ammonium lactate
Arginine PCA
Butylenes glycol
Cocamidopropyl Betaine
Copper PCA
Corn glycerides
Diglycereth-7 malate
Dimethyl imidazolidinone
Glucuronic acid
Glutamic acid
Honey extract
Hylauronic acid
Hydrololyzed wheat starch
Hydroxyethyl sorbitol
Lactic acid
Mineral oil
Polyglucuronic acid
Propylene glycerol
Saccharide hydrolysate
Sea salt
Seasame amino acids
Sodium aspartate
Sodium lactate
Sodium malate
Sodium PCA
Sodium polyaspartate
Triglycereth-7 citrate
EmollientEmollients help to fill in the spaces between the corneocytes in the cornified layer, they remain in the layer
Acetylated lanolin
Acetyl trihexyl citrate
Avocado sterols
Butyl myristate
C 14-15 alcohols
C 12-13 alkyl ethylhexonoate
Caprylyl glycol
Castor oil
Cetyl acetate
C 14-16 glycol palmitate
C 12-20 isoparaffin
Decyl oleate
Diethylhexyl adipate
Diethylhexyl malate
Diisodecyl adipate
Diisopropyl dilinoleate
Dimethicone copolyol
Dipropyl adipate
Ethylhexyl palmitate
Ethyl linoleate
Glyceryl dioleate
Glyceryl ricinoleate
Glyceryl stearates
Glycol palmitate (palm oil)
Glycine Soja (soybean oil)
Glycol stearate
Helianthus Annuus (sunflower) Seed oil
Hexyl laurate
Isocetyl alcohol
Isodecyl steararate
Isohexyl palmitate
Isopropyl isostearate
Isopropyl myristate
Isopropyl palmitate
Isosteryl alcohol
Jojoba oil
Methyl palmitate
Myristyl propionate
Octyl octanoate
Octyl stearate
PEG-4 lanolate
PEG-5 tristearyl citrate
Polyglyceryl-6 oleate
Plyclycerol-2 triisosterate
PPG-20 cetyl ether
PPG-4 laureth-2
Propylene glycol linoleate
Sucrose oleate
Sunflower seed oil glycerides
Tall oil glycerides
Tridycyl stearate
Wheat germ glycerides
Occlusives-Greasy ingredients that help to slow the evaporation of water from the skin, they are most effective when applied to damp skinAcetylated Castor Oil
Acetylated lanolin alcohol
Behenyl isosterate
Canola oil
Caprylic/capric triglyceride
Cetearyl methicone
Cetyl ricinoleate
Cholesteryl oleate
CyclomethiconeDecyl myristate
Disteryl ether
Glycol dioleate
Hexyldecyl isostearate
Hydrogenated castor oil
Hydrogenated lanolin
Isocetyl myristate
Lanolin linoleate
Lauryl Cocoate
Mineral oil- very frequently used due to it’s pleasant texture
Myristyl myrisstate
Neatsfool oil
Octyldodecyl stearate
Oleyl linoleate
Palm kernal wax
Petaerythrityl tetracocoate
Propylene glycol dioleate
Shark liver oil
Soybean lipid
Stearyl stearate
Tall oil
Trihexyldecyl citrate
Vegetable Oil

Guide to Face Wash, Eye Makeup Removers and more!
My complete guide to facial cleansing, including an overview on how cleansers work, common ingredients, product recommendations and tons of reviews!

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About Me

I’m a doctor, a mommy and a bit of a beauty addict. If you let me, I can take 2 hours to get ready in the morning. Really. I'm on a quest for faster beauty that works!

Leave a Comment


  1. 8.31.07
    Hanneri said:

    Thanx for a very informative post! I am going to bookmark it for future reference.

  2. 6.21.11

    Really such a nice and very impressive post. I was searching for this and got a total information in your post.

    Thanks a lot.

    Stacey Sharp
    Pro argi 9