Allergy to green kiwifruit has become common since the fruit was introduced in North America and Europe 30 years ago. Gold kiwifruit, more recently introduced commercially, has been shown to bind IgE from some individuals allergic to green kiwifruit. Hardy kiwifruit is a third species that is now cultivated in North America with potential application as a fresh fruit and in processed foods. To compare the IgE binding properties of proteins in hardy kiwifruit extract and processed hardy kiwifruit concentrate to each other and to extracts of green and gold kiwifruits to evaluate the potential for allergic cross-reactions. Sera from kiwifruit-allergic subjects and individuals without allergies to kiwifruit were assayed for IgE binding to soluble proteins in green, gold and hardy kiwifruits and heat-processed concentrate from hardy kiwifruit using immunoblots and direct enzyme-linked immunosorbent assay (ELISA). Marked IgE binding to specific hardy kiwifruit proteins was identified. However, IgE binding to heat-processed hardy kiwifruit concentrate was remarkably lower than to the raw fruit extract. These results suggest that some kiwifruit-allergic individuals may suffer allergic cross-reactions if they consume raw hardy kiwifruit. However, heat processing of the hardy kiwifruit alters allergenic protein structure, dramatically reducing in vitro IgE binding. Processing likely reduces the risk of eliciting an allergic response in those with allergies to raw kiwifruit.