Doctors originally believed ill health was linked to an imbalance between the elements of air, fire, water and earth in the body. This imbalance then led to excess blood. So 3,000 years ago, the Egyptians cut sick peoples’ veins to release blood. Blood letting was even used in the early 1800s, when leeches were applied to suck out blood from inflamed organs. By the mid 19th-century, however, studies exposed the practice as ineffective.