Human basophilic KU812F cells express a high-affinity immunoglobulin (Ig) E receptor, $Fc{varepsilon}RI$, which plays an important role in IgE-mediated allergic reactions. Houttuynia cordata Thunb (Family Saururaceae), which is rich in polyphenols, has been shown to have various physiological properties, including antiviral, antioxidative, anticancer, and anti-inflammatory activities. The effect of H. cordata extract on the expression of $Fc{varepsilon}RI$ in human KU812F cells was examined. Flow cytometric analysis showed that the $Fc{varepsilon}RI$ expression and the IgE binding activity were suppressed when the cells were cultured with H. cordata extract. Reverse transcription-polymerase chain reaction analysis showed that levels of the mRNAs for $Fc{varepsilon}RI{alpha}$- and $gamma$-chains were decreased by the treatment of H. cordata extract. Addition of H. cordata extract to culture medium was also observed to result in a reduction in the release of histamine from the cells. These results suggest that H. cordata extract may exert its anti-allergic activity through down-regulation of $Fc{varepsilon}RI$ expression and a subsequent decrease in histamine release.