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J. Cosmet. Sci., 75.5, 378–407 (September/October 2024)
*Address all correspondence to K. P. Anathapadmanabhan, ananthky@ucmail.uc.edu.
Interactions of Cosmetic Ingredients With Human Stratum
Corneum
K. P. ANANTHAPADMANABHAN
James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio, USA
Accepted for publication December 02, 2024.
Synopsis
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.
INTRODUCTION
The stratum corneum (SC) is the main barrier that prevents water loss from the body and
prevents the penetration of chemicals, pollutants, and germs into the body. Maintaining a
healthy SC is important not only for visibly good-looking skin, but also for ensuring overall
health and hygiene. The SC, however, is vulnerable to damage from changes in environmental
conditions, such as temperature and humidity, and from the chemicals and pollutants in the
atmosphere. Some chemicals, such as surfactants in cosmetic and personal care products,
can also lead to alterations in the properties of the SC, resulting in a weakening of the
barrier. A combination of factors—for example, a harsh cleanser with low temperature and/
or low humidity—can exacerbate the SC condition, resulting in a poor SC barrier. The
consequence of a poor skin barrier is the penetration of irritants into deeper layers, resulting
in a biochemical response from the body that often manifests as dry, itchy, and inflamed skin.
Ingredients found in moisturizers such as occlusives, humectants, and lipids can enhance
barrier properties. Selection of cosmetic ingredients based on an understanding of their
interactions with the SC barrier will help minimize and will even eliminate the harmful
effects of cosmetic ingredients on skin. In this review, the impact of some of the common
classes of chemicals used in cosmetic and personal care products and the ways to minimize
their damaging effect while maximizing their beneficial effects on the SC are discussed.