When a leech punctures the skin it anesthetizes the wound with its saliva, so that often the victim does not feel a thing. Also the leech's saliva dilates the blood vessels to increase blood flow and prevent the blood from clotting. This anticoagulant is called hirudin and has been used for medicinal purposes for centuries. Blood-letting with the aid of leeches reached its popularity in nineteenth century Europe. It was used to treat many ailments, including pain, skin disorders, and high blood pressure. A common treatment for headaches was to apply several leeches to each temple and allow them to remove the "tainted" blood. This leech craze contributed to the depletion of the European population of leeches.