Background and Objectives: Greek Philosopher Empedocles proposed theory of four elements and wrote that compounds are perishable. His theory is adopted by Philosophers and Physicians from Greece Rome and Arab like Hippocrates, Galen and Razes etc. They considered human body a compound too and explained the process of dissolution occurring in the body along with necessity of replenishment or nutrition to this dissolution or wear and tear. Methodology: This study is based absolutely on analysis of thought and doctrines of Unani physicians and philosophers regarding Tahallul (Dissolution) or wear and tear. Literature was surveyed from various classical Unani books and journals for better understanding and explanation of this concept. Collected material then analysed and systematized incomprehensive way. Interpretation and conclusion: According to Unani system of medicine human body is composed of four arkān (elements/primary constituents) which tend to get apart from the body. Also, during living processes and tasks dis solution occurs in the body due to various reasons but mainly due to ḥarāratgharīziyya (innate heat). Replenishment to this dissolution is mandatory. This replenishment is provided by food consumed in order to sustain life for a certain period.