Leech therapy, also known as hirudotherapy, is an ancient medical practice that involves the use of medicinal leeches (usually species of the genus Hirudo) to treat various medical conditions. This therapy has been used for centuries in traditional medicine systems such as Ayurveda and Unani, and it gained popularity in Europe during the medieval and early modern periods. Leeches are small, blood-sucking worms that secrete natural substances with anticoagulant, anti-inflammatory, and analgesic properties when they bite. These substances are believed to promote healing by improving blood circulation, reducing swelling, and alleviating pain.

In modern medicine, leech therapy is primarily used in the treatment of specific medical conditions, particularly those involving circulatory disorders, such as venous congestion, thrombosis, and reconstructive surgery. The saliva of leeches contains enzymes and compounds that prevent blood clotting, making them valuable in cases where blood flow needs to be improved or maintained, such as in the reattachment of severed body parts or the treatment of vascular diseases. Additionally, leech therapy has been explored as a complementary treatment for conditions such as osteoarthritis, inflammatory skin disorders, and certain types of headaches.