The effects of oral ingestion of a hot water extract of matured fruit of the date palm tree (Phoenix dactylifera L.) on allergic responses were investigated in mite-sensitized mice. Sneezing and nose rubbing events in mice given a date extract-added diet were significantly lower than in those given an extract-free (control) diet. The serum total and mite antigen-specific immunoglobulin (Ig) E levels, and the number of spleen interleukin-4⁺CD4⁺, IgE⁺B220⁺ and FcεRIα⁺CD117⁺ cells was significantly lower in mice given the date extract-added diet than in those given the control diet. Chlorogenic acid, pelargonin and ferulic acid significantly reduced the number of IgE⁺B220⁺ cells, while chlorogenic acid and pelargonin significantly decreased the number of FcεRIα⁺CD117⁺ cells in mouse spleen cell cultures. These results suggest that some polyphenols in the date may reduce mite-induced allergic symptoms in mice via a decrease in the number of IgE-producing plasma cells and high-affinity IgE receptor-expressing mast cells.