The effect of heat treatment on the IgE binding ability of ?-lactoglobulin, as pure protein or in whole milk, was studied by inhibition of IgE antibody binding using FEIA-CAP inhibition. A slight but significant decreased IgE binding was seen between unheated and heat-treated ?-lactoglobulin solution at 74 °C (IC50 = 2.03 and 3.59 ?g/mL, respectively, p = 0.032). A more pronounced decrease was found at 90 °C with an IC50 of 8.45 ?g/mL (p = 0.014). The inhibition of IgE binding of milk after heat treatment at 90 °C was also significantly decreased (p = 0.007). However, at all heat treatments, a similar total amount of IgE antibodies could be inhibited at a sufficiently high concentration of ?-lactoglobulin. The inhibiting ability of ?-lactoglobulin was significantly impaired in some fermented acidified milk products such as yogurt as compared to that in nonfermented milk (p < 0.001). There was only a small difference of IgE binding between the native forms of genetic variants A and B.