Cromolyn sodium is an anti-inflammatory medication. It works by preventing the release of substances in the body that cause inflammation. Cromolyn sodium nasal is used to prevent allergy symptoms such as runny nose, stuffy nose, sneezing, itching, and post-nasal drip. Cromolyn sodium nasal will not treat allergy symptoms that have already begun. The medication works best if used at least 1 week before you come into contact with things you are allergic to (pollen, dust, pets, etc). Cromolyn sodium nasal will not treat the symptoms of asthma, sinus infections, or the common cold. Cromolyn sodium nasal may also be used for purposes not listed in this medication guide.