As for internal bleeding leeches are considered very dangerous agents of it if they get inside the body, mostly around the throat and palate in the above-mentioned sources as well as in modern medicine: ???When they attach themselves to the epiglottis, trachea or bronchi, serious complications are likely??? http://www.itg.be/itg/distancelearning/lecturenotesvandenendene/52_Ectoparasitesp9.htm