What is acute hypersensitivity pneumonitis?

Inflammation in lung: Hypersensitivity pneumonitis is a lung disease in which an inhaled substance capable of triggering an immune response called and "antigen" is inhaled and causes an illness that is like pneumonia, with fever , shortness of breath etc.. Symptoms resolve when exposure to the antigen is stopped, but repetitive exposure can result in chronic scar formation in the lung. Steroid medicine can also help.