Hypersensitivity Pneumonitis is also called as extrinsic allergic alveolitis, is a pulmonary disorders resulted from immunologically induced inflammation of lung. This is a response to inhalation of foreign substances like chemicals, dust and molds which are called antigens. These may be organic or inorganic antigens that form haptens by sensitized individuals. Explore more about allergies Singapore visit http://www.naturaltherapies.com/allergies-2/