Antigenic proteins in latex products can cause type I allergy. We investigated the effects of potassium hydroxide (KOH) solution on the allergenicity of proteins in natural latex sap and latex gloves by using an EAST competitive inhibition immunoassay and skin prick test. Latex sap was mixed with KOH solution at different concentrations and incubated over various periods of time at room temperature. Latex gloves were washed in KOH solution for different times at 30°C and 90°C. Our immunoassay results for the subsequently extracted latex proteins demonstrated at KOH concentration-, temperature-, and time-dependent decrease in allergenicity, finally resulting in complete loss of IgE-binding activity. In the skin prick test, we found only four weakly positive reactions to proteins extracted from KOH-washed gloves in 30 latex-sensitized patients. In addition, up to 97% of the aqueous extractable protein content could be removed from latex gloves by washing in KOH solution under certain conditions. These results suggest that antigenic proteins in natural latex sap and latex gloves can be changed by treatment with KOH solution, which is followed by a loss of their capability to bind specific IgE antibodies from most latex-sensitized patients.