A series of eight patients admitted to a single-centre coronary care unit over a two-year period is described. All of the patients presented with an acute coronary syndrome within less than 48 h from the onset of an allergic reaction (six patients), or during an acute asthmatic paroxysm (two patients). None of the patients had any history of cardiac diseases, yet two had risk factors and two were former smokers. Four patients developed subendocardial myocardial infarction, three developed transmural myocardial infarction and one had unstable angina with no elevation in cardiac enzyme levels. Coronary angiograms were performed in seven of the eight patients; hemodynamically significant stenosis (greater than 70%) of one or more coronary arteries was detected in all patients. All seven patients underwent successful revascularization and recovered without complications. The present observational report hypothesizes that atopic people expressing an amplified mast cell degranulation may be more vulnerable to plaque rupture.