It is done either by venous section or by applying Leech.
Leech adhere to skin and sucks blood. Simultaneously it secrets a secretion along with saliva; called as hirudin. Hirudin dissolves impurities and clotted blood, which is removed from body by parallel blood sucking activity of leech.
In skin diseases, local lesions Leeches are preferred while in some joint diseases and systemic diseases having Rakta Dushti; Siravedha; venous section is preferred.
Siravedha means removal of Dushita Rakta by needle; promoting formation of fresh, Adushta Rakta!