Atopic dermatitis (AD) is a common condition in the pediatric population, affecting an estimated 15% of all children greater than 18 months of age in the United States. It is now recognized that AD is a disease of significant heterogeneity with respect to both disease severity and response to conventional pharmacologic therapies. With the recognition of this variability comes the understanding that, as with many other allergic disease, there exist many specific disease phenotypes that ultimately govern response to pharmacologic intervention. The characterization of these unique phenotypes and their associated biologic mediators is therefore of critical therapeutic importance in the development of disease and patient-specific treatment strategies.