Interactions of Cosmetic Ingredients With Human Stratum Corneum

The human stratum corneum (SC) is a physical barrier that prevents excessive water loss from the body and prevents the penetration of external pollutants and chemicals into the body. It is also a microbial barrier that prevents germs and microbes from entering the body. Skincare is all about protecting the SC barrier and ensuring its water holding and viscoelastic properties. The SC is routinely exposed to a wide range of chemicals including cleansing agents, moisturizers, and other advanced skincare products. Ingredients and products can interact with the SC barrier-some leading to weakening the barrier, and others to strengthening it. In this article, interactions of commonly used chemical ingredients with SC and their impact on SC barrier properties are reviewed, and approaches to identifying barrier-friendly ingredients are discussed.