We present, test, and extend a theoretical framework that connects disgust, a powerful basic human emotion, to political attitudes through psychological mechanisms designed to protect humans from disease. These mechanisms work outside of conscious awareness, and in modern environments, they can motivate individuals to avoid intergroup contact by opposing immigration. We report a meta-analysis of previous tests in the psychological sciences and conduct, for the first time, a series of tests in nationally representative samples collected in the United States and Denmark that integrate the role of disgust and the behavioral immune system into established models of emotional processing and political attitude formation. In doing so, we offer an explanation for why peaceful integration and interaction between ethnic majority and minorities is so hard to achieve.