The first staple in the skincare regimen is skin cleansing. A cleanser helps you wash away dirt and oil, and keep your face rejuvenating after removing the dead skin cells. The chemical group that you can find in every single cleanser is a surfactant.
What are surfactants?
Surfactants are amphiphilic compounds that contain a hydrophilic head (water-loving group) and a hydrophobic/lipophilic tail (oil-loving group). Surfactants reduce the interfacial tension between two immiscible liquids, liquid and a gas, or liquid and a solid.
For example, oil and water are very incompatible, they don’t like each other. A surfactant can disrupt the tension between these two and make them not repel each other in solution.
At a certain concentration in solution*, surfactants start to aggregate. The hydrophilic heads face outward while the lipophilic tails assemble in the center and together form a spherical shape called micelles.
*Critical micelle concentration (CMC)
We have heard a lot about micellar water in cosmetics. So how does the micellar water work?
Micellar water is made up of a bunch of micelle clusters suspended in water. When using micellar water on a cotton pad to remove make-up, the hydrophilic heads stick to the cotton while the lipophobic tails point out to the surface to grab dirt/oil/make-up and leave your skin clean.
There are four main types of surfactants that are commonly known, which are anionic, cationic, nonionic, and amphoteric surfactant.
Anionic: carrying negative charge of the head group, binding to the positive charge (+) particles like dirt and oil and creating a lot of foam. Anionic surfactants are used as primary surfactants in shampoos, soaps, shower gels…
Examples: Alkyl Sulfates, Alkyl Ether Sulfates, Acyl Sarcosinates, soap of fatty acids: Sodium Stearate…
I write a post about sulfate-free claims in this post.
Cationic: carrying positive charge of the head group. They are mainly used in hair conditioning products.
Examples: Cetrimonium Chloride, Distearyldimonium Chloride, Behentrimonium Chloride…
Nonionic: Carrying no charge of the head group, (they do not form ions in solution).
Because of containing no charge, nonionic surfactant is compatible with other types of surfactants and are milder in nature, which has minimal skin and eye irritation. Nonionic surfactants are majorly used as emulsifiers and co-surfactants.
Examples: Alcohol ethoxylates (such as Laureth-7…); fatty acid ethoxylates; sorbitan ester (such as sorbitan monolaurate, sorbitan monostearate, polysorbate…); ethoxylated glyceryl esters…
Amphoteric: carrying both charges (+) and (-) in the same molecule; their behavior depends on the pH of the solution. Amphoteric surfactants have low eyes and skin irritation, low toxicity, and are compatible with other types of surfactants. It is used as a co-surfactant and foam booster agent.
Examples: alkyl betaines (such as Lauryl Betaine), alkylampho(di)acetates, alkylampho(di)propionates.
Choosing facial cleansers?
I wrote about the skin structure in my previous post (here) The stratum corneum layer consists of dead keratinocytes, protein, lipids, and natural moisturizing factors (NMFs) which hydrate the skin and act as a protecting barrier for our body. Thus, a surfactant is used as an enhancer assisting in the skin-penetrating process, but it somehow messes up the structure of the skin. Surfactant in cleansers helps remove dirt/oil/makeup but also removes those important elements of our skin (proteins, lipids, and NMFs), for which you would feel your skin dehydrated and itching after cleansing your face with some types of strong cleansers.
Thus choosing a gentle facial cleanser is very important to keep your skin healthy.
A gentle facial cleanser should include milder surfactants, such as nonionic, and amphoteric surfactants. Those anionic surfactants can be harsh in facial cleansers. Of course, we need to look at the formulation as a whole to decide.
Skin pH is acidic (around 5) while most of the surfactant’s pH is high. Thus, it’s recommended that you should choose your cleanser with a lower pH (4-6). If the pH is not shown on the label, you can check with the pH indicator strip. If you don’t have the pH strips, you might need to do a little search on the products’ website.
Choose the cleanser that contains moisturizing agents and humectants such as glycerin, hyaluronic acid, and oil for softening effects.
You may not use soap for your face because it has high pH (main ingredient is lye NaOH), which can disrupt your skin layer.
Reference
Ingredient spotlight: Surfactants, stratiaskin.com
