Background. Allergic disorders such as atopic dermatitis (AD), allergic rhinitis, asthma, and food allergy show a predominant immune response by type 2 helper T (Th2) cells. We previously revealed that Rosae multiflorae fructus extract ameliorates ovalbumin-induced allergic rhinitis symptoms in a mouse model and identified miquelianin (quercetin 3-O-glucuronide, MQL) as the active compound. However, it is unknown if MQL affects allergic diseases or regulates Th2 immune responses. In this study, we investigated the anti-allergic effects of MQL. Methods. To investigate anti-allergic effects of MQL, we used an ovalbumin (OVA)-induced Th2-dominant mouse model and assessed cytokine production, cell proliferation, and upstream signaling pathways. Results. Oral administration of MQL suppressed the production of Th2 cytokines and IL-2, and cell proliferation. Additionally, heme oxygenase-1 (HO-1) expression was increased by MQL in splenocytes. In ex vivo studies using splenocytes and CD4+ T cells from mice, MQL suppressed Th1- and Th2-related immune responses by inhibiting CD4+ T cell proliferation. Furthermore, MQL increased HO-1 expression by activating the C-Raf -ERK1/2-NRF2 pathway by inducing the generation of intracellular reactive oxygen species in CD4+ T cells. Finally, to verify the effects of MQL in vivo during an allergic disorder, we used a trimellitic anhydride-induced AD-like mouse model. Both topical treatment and oral administration of MQL ameliorated AD symptoms by suppressing Th2 immune responses, including serum IgE production Th2 cytokine production in draining lymph nodes. Conclusions. MQL can be used as a therapeutic agent for CD4+ T cell-mediated diseases such as allergic diseases.