The skin is one of the largest immunologic organs in the body and a continuous target for allergic and immunologic responses. Impairment of the skin barrier increases the likelihood of external antigens and pathogens entering and creating inflammation, which can potentially lead to skin infections, allergies, and chronic inflammatory diseases such as atopic and contact dermatitis. Functionally, the skin barrier can be divided into four different levels. From outermost to innermost, these highly interdependent levels are the microbiome, chemical, physical, and immune levels.The objective of this review is to provide an update on current knowledge about the relationship between skin barrier function and how dysfunction at each level of the skin barrier can lead to allergic sensitization, contact dermatitis, and the atopic march, and examine how to best repair and maintain this barrier through the use of moisturizers.