List of products in the National Drug Code with proprietary name . This medication is used to treat certain allergic eye conditions (vernal keratoconjunctivitis, vernal conjunctivitis, vernal keratitis). It prevents itching of the eyes that can occur with these conditions. Cromolyn is known as a mast cell stabilizer. It works by blocking certain natural substances (histamine, SRS-A) that cause allergic symptoms.