Aerius is desloratadine, an anti-histamine that is used to relieve symptoms of allergy. ACC Long has acetylcysteine as the main ingredient; it belongs to the group of medications known as expectorants or mucolytics, because it helps dissolve all components that produce phlegm viscosity. This way, it loosens sputum and facilitates expectoration (spitting), so the irritating cough becomes less dry. 

These two medications are not related and do not interact with each other, so you can safely co-administer them.