The humoral theory plays a pivotal role in Unani System of Medicine and is the backbone of diagnosis and therapeutics of this system. Every human being is constituted of four basic humours i.e. Dam (Sanguine) ,Balgham (Phlegm), Safra (yellow bile) and Sauda (black bile) the predominance of one humour over other results in specifying the dominant temperament of an individual i.e. DAMVI (SANGUINE), BALGHAMI (PHELGMATIC), SAFRAVI(BILIOUS) SAUDAV(MELANCHOLIC). A vital power called Quwwat-e-Mudabbirah-e-badan maintains the equilibrium in the humours ensuring a healthy body and mind i.e. the homeostasis of the body is maintained. The disequilibrium results in illness and the imbalance is mainly due to weakening of the vital power by internal or external factors.