Kounis syndrome is a very rare syndrome which includes anaphylactic, anaphylactoid and hypersensitivity reactions accompanied with mast cell activation and acute coronary syndrome. In this case we aimed to define kounis syndrome. A 68 years old male patient applied to emergency department with back pain. After administration of the intramuscular analgesic; the patient suffered from symptoms such as dizziness, burning sensation all over the body. Patient was examined and blood pressure was 75/45 mmHg, heart rate was 90 beats/minute and respiratory rate was 14 /minute. The patient was detected with hyperemic skin and minimal uvular edema. Electrocardiography findings were ST segment elevations at derivations D2, D3, aVF, V5, V6 and ST segment depressions at derivations V1, V2, V3, D1, aVL. After percutaneous coronary angiography, coronary arteries were detected normal. The patient, newly diagnosed with acute coronary syndrome after allergen exposure, with positive skin findings and hypotension was evaluated as Kounis syndrome. There are 3 types of Kounis syndrome. These are defined as vasospastic allergic angina, allergic myocardial infarction and eosinophil and mast cell infiltration related stent thrombosis. The patient, without abnormal coronary arteries findings, was detected with coronary artery syndrome secondary to vasospasm. Increased exposure to allergens, increased awareness of physicians about Kounis syndrome, overconsumption of medicines contributes to increase this syndrome. The incidence of Kounis Syndrome has increasing but diagnosis of Kounis Syndrome is inadequate and easily overlooked. Most of all patients, presented with allergic reactions, should be evaluated for Kounis syndrome.