Typically Hirudo medicinalis are applied to draw blood and secrete saliva containing powerful anticoagulants (like hirudin), vasodilators and anti-inflammatory compounds. This combination not only prevents clotting and eases venous congestion but also boosts tissue perfusion and healing. Used since ancient Egyptian and Greek medicine and popular through the 19th century, it has seen a modern revival—especially in reconstructive and microsurgery—to relieve blood pooling, reduce swelling and promote recovery, blending time-honored practice with today’s clinical standards.