Nesajar is a nasal spray containing mometasone furoate, a corticosteroid used to treat the symptoms of allergic rhinitis (hay fever). It reduces inflammation inside the nasal passages, relieving congestion, sneezing, runny nose, and itching caused by both seasonal and year-round allergies. It’s approved for adults and children as young as 2 years old.
What Nesajar Treats
Nesajar’s primary use is managing allergic rhinitis, which comes in two forms. Seasonal allergic rhinitis is triggered by pollen during specific times of the year, while perennial (year-round) rhinitis is caused by ongoing exposure to allergens like dust mites, pet dander, or mold. Nesajar treats both.
Beyond treating active symptoms, mometasone furoate nasal sprays can also be used preventively. Starting the spray two to four weeks before allergy season begins can reduce or prevent symptoms from developing in the first place. This preventive use is approved for people aged 12 and older.
How It Works
When you inhale an allergen, your immune system launches a two-stage inflammatory response inside your nose. In the first stage (within about 30 minutes), your body releases histamine, which causes the immediate sneezing, itching, and runny nose. In the second stage (hours later), inflammatory cells and signaling molecules flood the nasal tissue, causing deeper congestion and swelling that can last much longer.
Mometasone furoate targets both stages. Clinical testing shows it significantly lowers histamine levels in nasal secretions during the early phase, reducing them from about 20 ng/mL to 14 ng/mL compared with placebo. During the later phase, it reduces the accumulation of inflammatory cells called eosinophils and lowers levels of key inflammatory signaling molecules. This dual action is what makes corticosteroid sprays more effective than antihistamine pills alone for many people with moderate to severe nasal allergies.
How Quickly It Works
Nesajar is not an instant-relief medication. Some people notice improvement within 12 hours of their first dose, about 28% in clinical trials compared to 13% on placebo. But the typical timeline for meaningful relief is longer. The median time to at least moderate symptom improvement is roughly 36 hours, and by 72 hours, about 64% of users experience noticeable relief. Full benefit builds over the first week or two of consistent daily use, so it’s important not to stop early if you don’t feel better right away.
Standard Dosing
For adults and children 12 and older, the typical dose is two sprays in each nostril once a day. Children aged 2 to 11 generally use one spray in each nostril once a day. The spray works best when used at the same time each day, and you should continue using it regularly through allergy season rather than only when symptoms flare.
Where It Fits in Allergy Treatment
The most recent international guidelines for allergic rhinitis management (ARIA 2024-2025) confirm that intranasal corticosteroids like mometasone furoate remain a cornerstone of treatment. The guidelines recommend them over intranasal antihistamines alone and suggest that combining a corticosteroid spray with an antihistamine spray may offer even better results for people whose symptoms aren’t fully controlled by either one. That said, the best approach depends on how severe your symptoms are, how they affect your daily life, and your personal preferences.
Common Side Effects
The most frequently reported side effects are local to the nose: dryness, soreness, and nosebleeds. These occur in more than 1 in 100 users. Headache is also common. If you experience recurring nosebleeds or persistent nasal irritation, stopping the spray for a few days and then restarting often helps. Tilting the nozzle slightly away from the center wall of your nose (the septum) when spraying can also reduce irritation.
Because mometasone furoate is applied directly to the nasal lining rather than taken as a pill, very little of it enters your bloodstream. This localized delivery is what gives corticosteroid nasal sprays a much more favorable side effect profile than oral steroids.
Long-Term Safety
People with year-round allergies often need to use their nasal spray for months or even years. A 12-month study specifically examined nasal tissue biopsies from patients using mometasone furoate daily at standard doses. The results were reassuring: there was no thinning of the nasal lining, no signs of tissue atrophy, and a decrease in abnormal cell changes (focal metaplasia) over the treatment period. Long-term daily use at recommended doses does not appear to damage the nasal tissue.
When to Use Caution
If you’ve recently had nasal surgery, a nose injury, or nasal sores or ulcers, mometasone furoate can slow healing in those areas. It’s best to wait until the tissue has recovered before starting the spray. You should also let your doctor know if you have an active infection, whether viral, bacterial, or fungal, since corticosteroids reduce local immune activity and can make it harder for your body to fight off infections in the nasal passages.