Cromolyn is a synthetic compound used to treat bronchospasms, or the narrowing of the airways, as well as allergic reactions. The mast cells, the cells that are present throughout the body and in the eyelids, lungs and nose, usually release chemicals that result in allergic reactions. As a mast stabilizer, Cromolyn stops the release of these chemicals by the mast cells. When inhaled, Cromolyn prevents episodes of asthma and the inflammation of the nose linings. As a solution, it treats inflammation of the lining of the eyelids and as an oral concentrate, it treats the condition of excessive mast cells.