The association between acute coronary events and acute allergic reactions has been recognized for several years. The first reported case occurred in 1950, during an allergic reaction to penicillin. In 1991, Kounis and Zavras described the syndrome of allergic angina and allergic myocardial infarction, currently known as Kounis syndrome. Two subtypes have been described: type I, which occurs in patients without predisposing factors for coronary artery disease and is caused by coronary artery spasm, and type II, which occurs in patients with angiographic evidence of coronary disease when the allergic events induce plaque erosion or rupture. This syndrome has been reported in association with a variety of medical conditions, environmental exposures, and medication exposures. Entities such as Takotsubo cardiomyopathy, drug-eluted stent thrombosis, and coronary allograft vasculopathy appear to be associated with this syndrome. In this review, we discuss the pathobiology, clinical features, associated entities, and management of Kounis syndrome.