Extrinsic Allergic Alveolitis (EAA) is a group of lung diseases that occur when someone becomes exposed to dust that is from either animals or plants originally. Extrinsic means that these diseases were caused by a source that is outisde of the body. An alveoli is an air sac in the lungs that exchanges oxygen for carbon dioxide. These diseases occur when someone is exposed to different types of dust for a long period of time. Nearly half of all people with EAA do not even show any symptoms. Symptoms include fever, muscle pain, cough, trouble breathing, sore throat, headache, and nausea. These symptoms can be anywhere from very intense to very mild. When a person is diagnosed, based upon their work history and level of exposure to particular forms of dust in combination with a showing of symptoms, thy are advised to avoid the dust. Avoiding the dust is usually the best cure, and breathing aid devices may be required if exposure had been very long and the condition is severe.