Tobacco worker’s lung is a condition marked by lung inflammation and subsequent scarring in the air sacs due to inhaling molds present in tobacco. It is not a lung infection but rather an immune reaction within the lungs to these molds. It is a type of hypersensitivity pneumonitis or extrinsic allergic alveolitis. The condition is also known as tobacco farmer’s lung but also occurs among tobaccos factory worker. Even though tobacco is commonly encountered in daily life, especially among tobacco users, this lung condition is almost entirely seen only in tobacco factory and farm workers. It is a result of a prolonged exposure to large amounts of tobacco dust with the airborne mold that the condition arises. Such large amounts is not encountered in daily life. Cigarette smoking may exacerbate tobacco worker’s lung but is not the cause of the condition.