Allergic reactions of the upper respiratory tract during use of powdered latex rubber gloves have been recently associated with sensitivity to latex. We have studied the ability of cornstarch powder to bind latex proteins and evaluated allergenic properties of the bound protein. Allergenicity was determined by competitive inhibition of human anti-latex IgE binding to solid-phase latex antigen. Cornstarch extracted from powdered latex products and clean cornstarch exposed to latex protein extracts were evaluated in comparison with clean unexposed cornstarch. Both exposed cornstarch preparations inhibited specific binding of anti-latex IgE antibodies to latex proteins in a dose-response manner. Latex-exposed cornstarch diluted 50% vol/vol produced complete inhibition, whereas greater dilutions exhibited variable levels of inhibition, depending on the source of cornstarch-bound proteins, insolubilized latex proteins, and IgE antibody-containing human serum used. Cornstarch not exposed to latex had no inhibitory activity. The study demonstrates that cornstarch indeed binds allergenic latex proteins and supports the causative relationship between allergic reactions in individuals with latex sensitivity and the exposure to airborne particles from powdered latex products.