Nasacort Allergy 24HR is an over-the-counter intranasal steroid (INS) used to treat nasal symptoms of indoor and outdoor allergies (perennial and seasonal allergic rhinitis). When Nasacort is used as directed, it can relieve the symptoms of allergic rhinitis (AR): sneezing, runny nose, nasal itching, and congestion.Nasacort is not for children under 2 years of age.