Hey, do you know SLS (Sodium Lauryl Sulfate) can disturb our skin as corona virus disturbing our this two years? Let see why SLS do this with our precious skin.....
Sodium lauryl sulfate [chemical formula C12H25SO4Na] also called sodium dodecyl sulfate or SLS, is an anionic surfactant. It lowers the interfacial tension and commonly used primary surfactant in cosmetic product but it is harsh in nature. Now coming to sodium lauryl ether sulphate it is also called as sodium laureth sulfate. The word “Laureth” serving as a contraction for the words “Lauryl” and “Ether.” SLES it is also anionic surfactant and less harsh than SLS.
Preparation
SLS is created by reacting lauryl alcohol with petroleum or with coconut or palm oil. SLS is modified to make Sodium Laureth Ether Sulfate. To derive SLES from SLS, a process called ethoxylation (in which ethylene oxide gas is introduced) has to take place. This process is key because it turns SLES into a safer, less harsh chemical than its predecessor i.e. SLS. Putting the SLS through the ethoxylation process led to the creation of SLES, often produces 1, 4-dioxane, a toxic contaminant and likely carcinogen.
Why SLS is Harsh on Skin?
here we can see how the surfactant interacts with stratum corneum during cleansing. Cleansers are usually formulated with a surfactant at a concentration much higher than its critical micelle concentration (CMC). At such concentration the majority of surfactant molecules self-assemble into micelles.
It is desirable for a cleanser to remove unwanted exogenous materials; however the interaction between surfactant and skin is more complicated. It has long been believed that only surfactant monomer can penetrate into the skin. Surfactant induce irritation is positively correlated with the CMC of surfactant mixtures and the CMC is the upper limit of monomer concentration in the solution. In addition, micelles were generally believed not able to penetrate into the skin due to their larger size.
The surfactant systems with low monomer concentrations or low critical micelles concentrations that were believe to be less irritating.
Personal care cleansers are primarily comprised of anionic surfactants and adding co-surfactant has reliably reduces their CMCs and lowers the aggressiveness of cleansers to the skin barrier.
SLS has small molecular structure and therefore it’s easily get penetrate to skin 5-6 mm below the applied site. Along with removing oil/ sebum SLS solubilize the lipid components such as lipid, enzyme and natural moisturizing factors weakens the skin barrier function.
Additionally surfactants can also remain in the SC even after rinsing and lead to chronic surfactant exposure. SC structure is composed of enucleated corneocyte embedded in an intracellular lipid matrix. These lipids from a highly order lamellar structure. Surfactant molecule that remains in the SC likely inserted into a lipid lamellae. The inserted surfactant disrupt SC lipid structured order and causes the continual degradation of the skin barrier. As the result of the barrier impairment, inflammation and oxidative stress occur, natural moisturizing factor loss which can then be perceived by patients as redness, dryness, discomfort, trans-epidermal water loss, irritation of the skin.
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