Gone are the days of harsh cleansers that dried out your skin – everyone’s getting into gentle cleansers! What’s the science behind gentle cleansing, and how do you pick a gentle cleanser? Here’s the scientific background behind this skin-loving trend!
Want more about the science behind choosing and using the right cleansers, moisturiser and sunscreen for your skin? Check out The Lab Muffin Guide to Basic Skincare!
How Cleansing Damages Your Skin
Cleansing is the most damaging thing you do to your skin on a daily basis, but unfortunately it’s necessary to get rid of all the dirt, makeup, oil and sunscreen you’ve accumulated on your skin over the course of the day. These unwanted substances won’t come off with water though! That’s why cleansers usually contain surfactants, magical chemicals which can help the grime dissolve in water and wash away.
Surfactants are the key ingredients in pretty much every single cleanser: foaming cleansers, soaps, body washes, cleansing balms, cleansing oils and micellar water. In fact, the only common surfactant-free cleansing methods I can think of are oil cleansing and using a cloth with just water. (I wrote about how surfactants are in everything in this post on The Toast a couple of years ago).
As amazing and useful as surfactants are at lifting grime, they’re not always good for your skin. The outer layer of your skin (the stratum corneum or SC) consists of dead, protein-rich skin cells filled with water-binding chemicals (your natural moisturising factor or NMF), surrounded by carefully arranged oily lipids (mostly ceramides, cholesterol and fatty acids). It looks a lot like a brick wall, with skin cell bricks and lipid mortar. Together, these form a barrier against water evaporating from the skin into the environment, and against external irritants entering your skin.
When the SC’s structure is disturbed, skin becomes dry, itchy, flaky, red and irritated. Luckily, the SC is pretty hardy and holds up well against most things… but unfortunately, surfactants are VERY good at messing things up! Here’s what a harsh cleanser does:
Removes important stratum corneum components
Surfactants are amazing at removing grime, but they can’t tell the difference between the chemicals that make up your skin and the chemicals that aren’t meant to be there. Surfactants are good at removing lipids (particularly cholesterol) from your SC, which messes up its structure and makes it more susceptible to water loss. They also remove proteins and NMF components from your skin, meaning it won’t be able to hold onto water as effectively. This all leads to dry, dehydrated skin.
Remains in the skin, causing irritation and disruption
After cleansing, most of the surfactant gets rinsed off, but unfortunately not all of it. Some surfactant molecules will bind to proteins in the skin, causing them to denature (change shape) and swell. The more swelling, the greater the irritation. (Interestingly, this interaction with proteins is probably a bigger contributor to the “tight” feeling after cleansing than the loss of oils!) Additionally, surfactants can remain in the lipid “mortar” of the SC, changing its structure. Together, these effects lead to a compromised SC that’s prone to letting water escape and irritants enter.