Dymista is a prescription medicine used to treat the symptoms of Seasonal Allergic Rhinits. Dymista may be used alone or with other medications. Dymista belongs to a class of drugs called allergy, Intranasal; Corticosteroids, Intranasal. It is not known if Dymista is safe and effective in children younger than 6 years of age. Dosage. The recommended dosage of DYMISTA is 1 spray in each nostril twice daily.