Dermatologists have known for decades that foaming agents break down barrier function in skin. As a matter of fact, sodium lauryl sulphate (SLS) has been used as the benchmark for irritating skin since the 1950s. A 1% solution of SLS left on skin will cause redness and irritation in pretty much everyone. It is one of the most common foaming agents in the world and together with the closely related sodium laureth sulphate (SLES) makes up the bulk of the global surfactant market.
The skin’s primary function is to keep the outside out. Breakdown of barrier function results in constant triggering of the immune system as pathogens and irritants make it past the stratum granulosum.
SLS and SLES have come under fire in the past for disrupting barrier function and allowing penetration of other toxic ingredients in skincare products.
In the same skin irritation test mentioned above, water is used as the negative control. It almost never causes skin irritation. Maybe we should try that for a while?
