Atopic dermatitis is a pathology associated with a dysfunction of the skin barrier, excessive colonization of the Staphylococcus aureus bacteria and anomalies affecting the immune system. 
A study was published in 2015 in the Plos One journal (Impact Factor: 2.766) and showed the role played by commensal flora in the regulation of our immune responses. 
S. epidermidis, the bacteria most representative of commensal flora, has an anti-inflammatory effect which counters that of inflammatory S. aureus, meaning that S. epidermidis has an immunomodulatory effect.