Hi Ms. Smith,   Bronchiolitis is mostly diagnosed in young children (infants and toddlers). Viral infections are the cause of bronchiolitis in many cases. Bronchioles are the tiny airways in the lung that direct airflow to the areas of the lung where oxygen is exchanged for carbon dioxide. When they become inflamed the term bronchiolitis is used.   In adults bronchiolitis has different causes that are often not well understood. Reversible obstruction of the lung is reported (similar to asthma). Many people respond well to oral or infused steroids.   Some occupational related exposures to mold and toxins may cause bronchiolitis because of an intense immune reaction that occurs in the bronchioles.   You may have a more acute form of bronchiolitis caused by an unidentified virus or bacteria.   Asthma is an inflammatory lung disease that involves inflammation of a broader region of the lung airway. Inflammation is not limited to the bronchioles (inflammation occurs along the entire airway of the lung). Asthma is a chronic disease highlighted by a significant degree of reversibility (especially with treatment) and persistent hyper-responsiveness of the bronchi (twitchy airways).   Sometimes it is difficult to separate bronchiolitis from asthma. This is why bronchoscopy or open lung biopsy may be considered.   Hope you continue to do well.   J. Thompson, MD