Medicinal leeches are as old as the Pyramids. Records indicate that Egyptians used leech therapy over 3,500 years ago and leeches (often mistakenly credited as cobras) are included in the hieroglyphics painted on the walls. Leech therapy was used to treat a wide range of conditions, from headaches to hemorrhoids.  
Bloodletting is one of the oldest medical practices, having been practiced since ancient times, including the Mesopotamians, the Greeks, the Mayans, and the Aztecs. In Greece, bloodletting was standard practice around the time of Hippocrates and Herophilos.

Herophilos (335-280 BC) was a Greek physician who was the first scientist to systematically perform scientific dissections of human cadavers and is deemed to be the first anatomist. Hippocrates of Cos (460BC-370BC) was also a Greek physician and is referred to as the “father of medicine”. He was the first physician to reject superstitions, legends and beliefs that credited supernatural or divine forces causing illness.

Both physicians used medicinal leeches, amongst other methods, for blood letting to remove blood from a patient to “balance the humours”. The four humours of ancient medical philosophy were blood, phlegm, black bile and yellow bile. The belief at the time was that these four humours must be kept in balance in order for the human body to function properly. Any disease or illness was thought to be a result of an imbalance of these humours. The dominant humour was believed to be blood.

However it was Aelius Galenus (AD 129 – 200), a prominent physician and philosopher and the most accomplished medical researcher of the Roman era who practiced blood letting extensively and introduced blood letting to Rome. His theories dominated and influenced Western medical science for well over a millennium. Of the four humours, Galen believed that blood was the dominant humor and the one in most need of control. Romans were the first to use the HIRUDO name for leeches.