The methods and compositions described herein are based, in part, on the discovery of a polypeptide of soluble CD23 (sCD23) that binds and sequesters IgE. Thus, the sCD23 peptides, polypeptides and derivatives described herein are useful for treating conditions or disorders involving increased IgE levels such as e.g., allergy, anaphylaxis, inflammation, lymphoma, and certain cancers.