Atopic dermatitis (AD) is a chronic skin disease characterized by inflammation and disruption of the skin barrier. It is normally treated using moisturizers and steroids; however, these are palliatives and do not serve as a therapy. Mesenchymal stem cells (MSCs) are tissue stem cells with immunomodulatory activities, and exosomes are extracellular vesicles that reflect the physiologies of producer cells. Therefore, the use of MSCs and exosomes with their immunomodulatory activities is emerging as a new method to treat AD. Here, we used cobalt chloride (CoCl 2 ) to induce hypoxic conditioning, and tested the therapeutic efficacy of exosomes derived from CoCl 2 -treated MSCs in treating AD. In vitro , the exosomes derived from CoCl 2 -treated MSCs increased the proliferation of HaCaT cells and decreased inflammatory cytokine levels. In the oxazolone-induced chronic AD mouse model, the exosomes derived from CoCl 2 -treated MSCs reduced ear thickness, restored the skin barrier, and reduced immune cell infiltration and inflammatory markers. These data indicated that hypoxic conditioning induced by the CoCl 2 treatment enhanced the therapeutic efficacy of exosomes derived from MSCs, suggesting that these exosomes can be used to alleviate the symptoms of AD.