Maxillary sinusitis is inflammation or infection of the maxillary sinuses, the pair of air-filled cavities sitting behind your cheekbones on either side of the nose. It is the most common form of sinusitis because the maxillary sinuses are the largest of the four paired sinus groups and their drainage opening sits near the top of the cavity rather than at the bottom, making them especially prone to fluid buildup. The condition ranges from a short-lived infection after a cold to a stubborn chronic problem that lingers for months, and the causes, symptoms, and treatment differ meaningfully depending on which form you have.
Why the Maxillary Sinuses Are So Vulnerable
Your sinuses are lined with a thin mucous membrane that produces a continuous film of mucus. Tiny hair-like structures called cilia sweep that mucus toward a small drainage channel called the ostiomeatal complex, which connects the sinus to the nasal passage. When everything works, mucus drains smoothly, bacteria get flushed out, and air circulates freely. The ostiomeatal complex is the bottleneck: it serves the maxillary, frontal, and anterior ethmoid sinuses all at once, and if it swells shut, those sinuses lose both ventilation and drainage.1PubMed Central. Osteomeatal Complex: A Study of Its Anatomical Variation Among Patients Attending North Bengal Medical College and Hospital
The maxillary sinus has an additional design problem. Its drainage opening is located high on the inner wall of the cavity, which means gravity works against drainage. Mucus, pus, and fluid pool at the floor of the sinus rather than flowing naturally toward the exit. That pooling creates a warm, moist environment where bacteria thrive, and it explains why the maxillary sinus gets infected more often than the others.
Children’s sinuses develop gradually. The maxillary and ethmoid sinuses are present at birth but small, reaching full size around age twelve. The frontal and sphenoid sinuses do not even begin meaningful development until age two or three and may not be fully formed until the late teens or early twenties.2PubMed Central. Acute bacterial sinusitis in children: an updated review This matters because children’s smaller sinuses and narrower drainage pathways can obstruct more easily, yet certain sinus types simply aren’t involved in young children because they haven’t formed yet.
Causes of Acute Maxillary Sinusitis
Most acute cases begin with a viral upper respiratory infection, an ordinary cold. The virus inflames the nasal and sinus lining, the ostiomeatal complex swells, and mucus stagnates. In the majority of people the inflammation resolves on its own within a week or two. In a smaller subset, bacteria colonize the stagnant mucus and a secondary bacterial infection develops. You can often tell the difference by timing: viral sinusitis peaks around days three to five and then gradually improves, while bacterial sinusitis either persists beyond ten days without improvement or gets worse after an initial partial recovery.
The bacteria most often responsible for acute bacterial sinusitis in both adults and children are Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pyogenes.3PubMed. Microbiology of sinusitis Studies that cultured sinus fluid directly from the maxillary sinus in young adults found H. influenzae in about half of positive cultures and S. pneumoniae in roughly a fifth.4PubMed Central. Bacteriological findings of acute maxillary sinusitis in young adults In patients with untreated acute sinus infections, pathogens were recovered in the vast majority of cases, with S. pneumoniae being the single most common organism.5PubMed. Bacteriology of maxillary sinusitis in relation to character of inflammation and prior treatment
Allergies, nasal polyps, a deviated septum, and other sources of chronic nasal obstruction all raise your risk because they narrow the drainage pathway even before a cold arrives. Smoking, swimming in chlorinated pools, and immune suppression are additional risk factors. Anything that impairs the mucociliary system or blocks the ostiomeatal complex sets the stage.
The Dental Connection
The floor of the maxillary sinus sits directly above the roots of your upper back teeth. In some people the roots actually poke through the bone into the sinus lining. That proximity creates a pathway for dental infections, failed root canals, tooth extractions, and even implant procedures to seed bacteria directly into the sinus. This is called odontogenic sinusitis, and it accounts for close to 30% of cases when only one maxillary sinus is inflamed.6PubMed Central. Odontogenic maxillary sinusitis: A comprehensive review
What makes odontogenic sinusitis distinct is the microbiology. Rather than the typical respiratory bacteria, the infections tend to be mixed with a heavy presence of anaerobic organisms, the same bacteria found in dental plaque and biofilm. Porphyromonas, Prevotella, and Fusobacterium species dominate, and they degrade mucin in ways that fuel ongoing mucosal inflammation.7Scientific Reports. Microbiota dysbiosis in odontogenic rhinosinusitis and its association with anaerobic bacteria Standard sinus antibiotics aimed at the usual respiratory pathogens often miss these organisms entirely, which is one reason dental-origin sinusitis tends to resist conventional treatment. A review of the literature found that infections are often polymicrobial and require antimicrobial choices that specifically cover anaerobes.8PubMed Central. Odontogenic sinusitis: A review of the current literature
If your doctor treats one-sided maxillary sinusitis with antibiotics and it keeps coming back, an unrecognized dental cause is one of the first things to investigate. Missing the dental source usually leads to chronic, treatment-resistant disease.6PubMed Central. Odontogenic maxillary sinusitis: A comprehensive review
Chronic Sinusitis and Nasal Polyps
When maxillary sinusitis lasts twelve weeks or longer, it is classified as chronic rhinosinusitis. The causes shift. While acute sinusitis is usually about a single bacterial or viral infection, chronic disease involves a sustained inflammatory process in which a defective sinus lining, repeated exposure to colonizing bacteria, and an overreactive immune response all feed each other.9PubMed Central. Chronic Rhinosinusitis with Nasal Polyps
A subset of chronic sinusitis patients develop nasal polyps, soft growths that hang from the sinus or nasal lining and obstruct drainage further. This form is driven predominantly by type 2 inflammation, which leads to tissue remodeling and polyp formation.10Alergoprofil. Treatment of chronic sinusitis with nasal polyps People with nasal polyps tend to have more severe symptoms, higher rates of recurrence after surgery, and a stronger association with asthma.
Fungal Sinusitis
Fungi can also set up shop in the maxillary sinus. In people with healthy immune systems, the most common form is a fungal ball, a dense clump of fungal material (usually Aspergillus) that grows inside the sinus without invading tissue. A fungal ball is non-invasive and typically treated with surgical removal rather than antifungal drugs.11PubMed. Concurrent diagnosis of sinus fungus ball and invasive fungal sinusitis: A retrospective case series
The picture changes in immunocompromised people, including those undergoing chemotherapy, organ transplant recipients on immunosuppressive drugs, and patients with uncontrolled diabetes. In these patients, fungal sinusitis can become invasive, meaning the fungus penetrates the sinus wall and spreads into surrounding bone, the orbit, or even the brain. Invasive fungal sinusitis carries high mortality and demands aggressive antifungal therapy and surgery. Even a non-invasive fungal ball can transform into invasive disease in the immunocompromised, making close follow-up essential.12Proceedings of Singapore Healthcare. Transformation of a maxillary paranasal sinus fungal ball into a mass-like form of invasive fungal sinusitis in the immunocompromised host
Symptoms and How It Is Diagnosed
The hallmark symptoms of maxillary sinusitis are facial pain or pressure centered over the cheek, nasal congestion, and thick discolored nasal discharge. Pain that worsens when you bend forward is a classic sign. Other common complaints include toothache in the upper teeth, a reduced sense of smell, postnasal drip, and sometimes a low-grade fever. A study comparing symptoms to ultrasound-confirmed maxillary sinusitis found that the combination of a preceding cold, thick discolored nasal discharge, pain on bending, one-sided cheek pain, and tooth pain were the symptoms most strongly associated with a positive diagnosis.13PubMed. Use of symptoms and signs to diagnose maxillary sinusitis in general practice: comparison with ultrasonography
Most acute cases are diagnosed clinically, meaning your doctor decides based on symptoms and a physical exam rather than ordering imaging right away. A CT scan is considered the gold standard for sinus imaging and is typically reserved for cases that don’t respond to initial treatment, or when chronic sinusitis or complications are suspected.14PubMed Central. Nasal Endoscopy as an Effective Alternative for CT-Scan in Diagnosing Chronic Rhinosinusitis: A Clinical Study and Review of Literature Nasal endoscopy, where a thin camera is inserted into the nose, provides a direct view of the drainage pathways and can identify polyps, pus, or swelling without radiation. Studies have shown good agreement between endoscopy and CT findings, and endoscopy can spare patients unnecessary scans and the associated cost and radiation.15PubMed Central. Comparative Study of Diagnostic Nasal Endoscopy and CT Paranasal Sinuses in Diagnosing Chronic Rhinosinusitis16PubMed. Diagnosis of surgical sinusitis using nasal endoscopy and computerized tomography
Medical Treatment
Treatment depends on whether you are dealing with an acute episode or a chronic condition, and whether the cause is viral, bacterial, dental, or fungal.
Acute Viral Sinusitis
Because most acute sinusitis starts with a virus, antibiotics do nothing for it. The standard approach is supportive care: saline nasal rinses to flush mucus, decongestants for short-term relief, and pain relievers. Most viral episodes clear within seven to ten days. Antibiotics are warranted only when symptoms persist beyond ten days without improvement, worsen after initial improvement, or are unusually severe from the start with high fever and purulent discharge.
Acute Bacterial Sinusitis
When antibiotics are indicated, amoxicillin or amoxicillin-clavulanate is the usual first choice. Treatment guidelines rank antibiotics by predicted effectiveness against the common sinus pathogens. High-dose amoxicillin-clavulanate and respiratory fluoroquinolones top the list at roughly 90% predicted efficacy, while standard-dose amoxicillin and several cephalosporins fall in the mid-80s.17PubMed Central. Antimicrobial treatment guidelines for acute bacterial rhinosinusitis Fluoroquinolones are generally reserved for patients with allergies or treatment failures because of concerns about resistance and side effects. For odontogenic cases, remember that anaerobic coverage is critical, so amoxicillin-clavulanate or clindamycin tend to be better choices than amoxicillin alone.8PubMed Central. Odontogenic sinusitis: A review of the current literature
Chronic Sinusitis
Chronic maxillary sinusitis requires a different strategy. Intranasal corticosteroid sprays are the backbone, reducing the inflammation that keeps the cycle going. Various delivery methods, including standard sprays, nebulization, and high-volume saline irrigation mixed with a corticosteroid, are used to improve how well the medication reaches the sinus lining.18The Journal of Allergy and Clinical Immunology: In Practice. Medical Management Strategies in Acute and Chronic Rhinosinusitis Saline irrigation on its own also helps by physically clearing mucus and inflammatory debris.
For chronic sinusitis with nasal polyps that does not respond to topical steroids and surgery, biologic medications have become an option. Dupilumab, which blocks a key inflammatory pathway involved in polyp formation, became the first biologic approved for chronic sinusitis with nasal polyps in 2019. Other biologics targeting related pathways have followed.18The Journal of Allergy and Clinical Immunology: In Practice. Medical Management Strategies in Acute and Chronic Rhinosinusitis These drugs are expensive and reserved for difficult cases, but they represent a real shift for patients who previously had no good options between corticosteroids and repeated surgery.
When Surgery Is Needed
Functional endoscopic sinus surgery, known as FESS, has largely replaced older open procedures for chronic or recurrent maxillary sinusitis.19PubMed. Endoscopic sinus surgery or Caldwell-Luc operation in the treatment of chronic and recurrent maxillary sinusitis The goal is to widen the natural drainage opening of the maxillary sinus and remove any polyps, fungal material, or damaged tissue blocking it. FESS is done entirely through the nostrils, with no external incisions.
Long-term outcomes are encouraging. A ten-year prospective study found that quality of life improved significantly within six months of surgery and that improvement held steady over the full decade. More than three quarters of patients reported lasting benefit. The revision surgery rate was about 17% over ten years, rising to 25% in patients with nasal polyps. Satisfaction was high, with most patients saying they would have the surgery again.20PubMed Central. Long-term outcomes of endoscopic sinus surgery in the management of adult chronic rhinosinusitis
Airflow modeling shows that FESS substantially increases ventilation of the maxillary sinus. After surgery, average airflow velocity into the sinus more than quadrupled compared with pre-surgical levels.21PubMed Central. Quantification of airflow into the maxillary sinuses before and after functional endoscopic sinus surgery That improved airflow also makes topical medications more effective because they can actually reach the sinus lining. Modeling of post-surgical drug delivery suggests that larger surgical openings generally improve medication deposition, though the optimal particle size for sprays or nebulizers falls in a relatively narrow range, roughly five to twenty micrometers.22PubMed Central. A computational study of functional endoscopic sinus surgery and maxillary sinus drug delivery
Treating Odontogenic Sinusitis Requires Two Specialists
When the maxillary sinus infection originates from a dental problem, neither sinus surgery alone nor dental treatment alone is reliably effective. Both the sinus inflammation and the underlying dental pathology need to be addressed. Treatment can include root canal therapy, periodontal treatment, extraction of the offending tooth, repair of any fistula between the mouth and sinus, and sinus surgery if medical therapy fails to resolve the inflammation. Expert consensus stresses that an ear-nose-throat specialist and a dental provider should collaborate on treatment decisions.23International Journal of Oral Science. Expert consensus on odontogenic maxillary sinusitis multi-disciplinary treatment24PubMed. Management of odontogenic sinusitis: multidisciplinary consensus statement
A significant portion of odontogenic sinusitis patients still require FESS even after the dental source is dealt with, because the sinus inflammation can become self-sustaining once established.8PubMed Central. Odontogenic sinusitis: A review of the current literature If you have been told you need sinus surgery for one-sided maxillary disease, it is worth asking whether a dental evaluation has been done.
Complications to Watch For
Serious complications from sinusitis are uncommon, but they do happen and can be life-threatening. The sinuses sit close to the eye sockets and the brain, so infection can spread to those areas. Possible complications include orbital cellulitis or abscess (infection around the eye), brain abscess, subdural empyema (a pus collection between the brain and its covering), epidural abscess, meningitis, and venous sinus thrombosis (a blood clot in the veins draining the brain).25PubMed. Neurological Complications of Acute and Chronic Sinusitis
Warning signs that warrant urgent medical attention include swelling or redness around the eye, changes in vision, severe headache, high fever, confusion, or neck stiffness. These complications typically require both intravenous antibiotics and surgical drainage of the sinus and any abscess that has formed.26PubMed Central. Management Strategy of Intracranial Complications of Sinusitis: Our Experience and Review of the Literature While rare, the potential severity is the reason doctors take sinusitis that worsens rapidly or does not respond to treatment very seriously.
Air Pollution and Chronic Sinus Disease
There is growing evidence that air quality plays a role in chronic sinusitis beyond what most people realize. A systematic review found that even modest increases in fine particulate matter were linked to substantially higher odds of being diagnosed with chronic sinusitis, with the association strongest for severe disease involving multiple sinuses.27PubMed Central. Environmental air pollution and chronic rhinosinusitis: A systematic review Research tracking chronic sinusitis patients over time found that symptom scores worsened during periods of higher ozone and particulate pollution, particularly during warmer months.28PubMed Central. Association between outdoor air pollution and chronic rhinosinusitis patient reported outcomes
This does not mean pollution directly causes sinusitis the way bacteria do. But it does suggest that if you have chronic sinus problems, living or working in areas with poor air quality can worsen your symptoms and make the disease harder to control. Practical steps like using a HEPA filter indoors, checking air quality indices before spending extended time outdoors, and wearing a mask on high-pollution days are reasonable for people whose sinuses are already vulnerable.
How Chronic Sinusitis Affects Daily Life
People who have never had more than a brief sinus infection sometimes underestimate how debilitating chronic sinusitis can be. Research consistently shows that chronic rhinosinusitis produces measurable, significant drops in health-related quality of life.29PubMed. Quality of life in patients with chronic rhinosinusitis The impact is comparable to other chronic diseases in terms of how much it interferes with daily functioning, work productivity, and emotional well-being.
Among the various symptom domains, facial pain and ear discomfort have the largest impact on overall quality of life, followed closely by sleep disruption. The nasal symptoms themselves, congestion and discharge, actually rank lowest in terms of how much they affect general well-being, which may be surprising given that they are the most visible symptoms.30PubMed. Symptoms of chronic rhinosinusitis differentially impact general health-related quality of life Chronic pain and poor sleep are what wear people down. Understanding this can help patients communicate more effectively with their doctors about what is actually bothering them most, rather than focusing only on the stuffiness that feels most obviously “sinus-related.”