Mometasone furoate nasal spray (MFNS) is a once-a-day product. This is a multi-center, open-label study of MFNS in children with perennial allergic rhinitis. MFNS will be administered to pediatric subjects (3-15 years old) with perennial allergic rhinitis at a dose of 100 to 200 μg/day (once daily) for 12 weeks. Subjects (subject's legal representatives) provided consent to continue treatment beyond 12 weeks will receive treatment for up to 24 weeks. At each clinic visit, observation of adverse events, nasal symptom scores, and nasal findings will be evaluated. The presence/absence of serious adverse events and trial procedure-related AEs will be reviewed 30 days after the end of the follow-up.

Inclusion Criteria:

• Subjects having symptoms of perennial allergic rhinitis of moderate to severe degree.
• Subjects confirmed to be allergic to non-seasonal environmental antigens (e.g., house dust mite antigen).
• Male or female outpatients aged 3 to 15 years at the time of providing informed consent.

Exclusion Criteria:

• Subjects with coexisting tuberculosis or lower respiratory tract infection, or who have an acute upper respiratory tract infection or acute pharyngolaryngitis, etc. judged by the investigator to require treatment at the time of registration
• Subjects with coexisting infections or systemic mycosis for which there are no effective antibiotics
• Subjects with repeated epistaxis
• Subjects with coexisting fungal infection in nasal/sinus cavity
• Subjects with a history of hypersensitivity to steroids or ingredients of mometasone furoate nasal spray
• Subjects with severe hepatic, renal, cardiac, hematological disease, diabetes mellitus, hypertension, or other serious coexisting diseases and whose general condition is poor.
• Subjects allergic to pollen (cedar, Japanese cypress, birch, grasses, mugwort, common ragweed, etc.) for whom the pollen season coincides with the observation period