Leeches have been used in medicine for centuries and were first employed in Egypt about 2500 years ago. Today they are often used in plastic surgery, because natural anticoagulant they secrete fights blood clots and resorts proper blood flow to inflamed parts of body.

   Medical leeches have been found to secrete saliva containing 60 different proteins. These achieve a wide variety of goals useful to the leech as it feeds, helping to keep the blood in liquid form and increasing blood flow in the effected area. It is also thought that the saliva contains an anaesthetic, as leech bites are generally not painful.