background: The efficacy assessment of human anti-IgE monoclonal antibodies (mAbs) in animal models before clinical trials is hampered due to the lack of cross-reactivity of anti-IgE mAbs between species. objective: We developed CRE-DR (an anti-dog IgE monoclonal antibody), an anti-IgE mouse mAb that recognizes canine and human IgE, and then examined its IgE specificity and cross-reactivity between three animal and human species. methods: After mouse immunization with a synthetic peptide derived from canine IgE ( NTNDWIEGETYYC ), we generated a hybridoma producing CRE-DR. The CRE-DR purified from the ascites of hybridoma-inoculated mice was used for ELISA and Western blot analysis to examine reactivity to dog, human, and rodent IgEs as well as recombinant bovine serum albumin (BSA)-conjugated to canine, human, and rodent IgE amino acid peptides corresponding to the immunizing sequence. We then performed enzyme-linked immunosorbent assays (ELISAs) for dog IgE using sera from dogs with atopic dermatitis (AD) after inhibition with canine IgE and IgG. The amino acid sequence recognized by CRE-DR was identified by ELISA using synthetic peptides. results: CRE-DR is a monoclonal mouse IgG1κ specific for dog IgE, and the ELISA values in atopic dog sera were inhibited by dog IgE, but not dog IgG. The binding of CRE-DR to human IgE was relatively maintained, but not to rodent IgEs, which results were confirmed with the BSA-conjugated IgE peptides of the various species. The CRE-DR reactivity was supported by the comparison of amino acid sequence of CRE-DR epitope, DWIEGETYYC, in dog IgE; one, two, and three amino acids were substituted in the human, rat, and mouse IgE epitopes, respectively. conclusions: CRE-DR is a mAb cross-reactive to dog and human IgEs, which can allow the use of a dog model of allergy to test the efficacy of a CRE-DR-derived anti-IgE therapeutic mAb before human clinical trials.