Angiography is a medical imaging technique used to visualize blood vessels in the brain, neck, heart, and kidneys. For this technique, radiopaque substances and dyes are used to make the blood vessels visible under x-ray. Angiography is used to detect abnormalities or blockage in blood vessels. This, in turn, helps diagnose various critical conditions such as heart diseases, kidney disorders, kidney dysfunction, atherosclerosis, brain tumors, and eye diseases. Moreover, angiography helps surgeons study the condition of the heart and brain before surgeries. There are several types of angiography which are categorized based on the blood vessel analyzed. Major types of angiography include coronary angiography, pulmonary angiography, kidney angiography, fluorescein angiography, celiac angiography, and mesenteric angiography. There are some side-effects of angiography noticed in some patients. These are mainly allergic reactions caused by the substances and dyes used in angiography. Major allergic reactions include swelling, breathing problems, heart failure, and low blood pressure.