Merck Manual

Please confirm that you are a health care professional

honeypot link



Marvin P. Fried

, MD, Montefiore Medical Center, The University Hospital of Albert Einstein College of Medicine

Reviewed/Revised Jul 2023
Topic Resources

Sinusitis is inflammation of the paranasal sinuses due to viral, bacterial, or fungal infections or allergic reactions. Symptoms include nasal obstruction and congestion, purulent rhinorrhea, and facial pain or pressure; sometimes malaise, headache, and/or fever are present. Treatment of presumed viral acute rhinitis includes steam inhalation and topical or systemic vasoconstrictors. Treatment of suspected bacterial infection is with antibiotics, such as amoxicillin/clavulanate or doxycycline, given for 5 to 7 days for acute sinusitis and for up to 6 weeks for chronic sinusitis. Decongestants, corticosteroid nasal sprays, and application of heat and humidity may help relieve symptoms and improve sinus drainage. Recurrent sinusitis may require surgery to improve sinus drainage.

Sinusitis may be classified as acute (completely resolved in < 30 days); subacute (completely resolved in 30 to 90 days); recurrent (≥ 4 discrete acute episodes per year, each completely resolved in < 30 days but recurring in cycles, with at least 10 days between complete resolution of symptoms and initiation of a new episode); and chronic (lasting > 90 days).

Etiology of Sinusitis

Acute sinusitis in immunocompetent patients in the community is almost always viral (eg, rhinovirus, influenza, parainfluenza). A small percentage develop secondary bacterial infection with streptococci, pneumococci, Haemophilus influenzae, Moraxella catarrhalis, or staphylococci. Occasionally, a periapical dental abscess of a maxillary tooth spreads to the overlying sinus. Hospital-acquired acute infections are more often bacterial, typically involving Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, and Enterobacter. Immunocompromised patients may have acute invasive fungal sinusitis (see Sinusitis in Immunocompromised Patients Invasive Sinusitis in Immunocompromised Patients Sinusitis is inflammation of the paranasal sinuses due to viral, bacterial, or fungal infections or allergic reactions. Symptoms include nasal obstruction and congestion, purulent rhinorrhea... read more Invasive Sinusitis in Immunocompromised Patients ).

Chronic sinusitis involves many factors that combine to create chronic inflammation. Chronic allergies, structural abnormalities (eg, nasal polyps), environmental irritants (eg, airborne pollution, tobacco smoke), mucociliary dysfunction, and other factors interact with infectious organisms to cause chronic sinusitis. The organisms are commonly bacterial (possibly as part of a biofilm on the mucosal surface) but may be fungal. Many bacteria have been implicated, including gram-negative bacilli and oropharyngeal anaerobic microorganisms; polymicrobial infection is common. In a few cases, chronic maxillary sinusitis is secondary to dental infection. Fungal infections (Aspergillus, Sporothrix, Pseudallescheria) may be chronic and tend to strike older and immunocompromised patients.

Allergic fungal sinusitis is a form of chronic sinusitis characterized by diffuse nasal congestion, markedly viscid nasal secretions, and, often, nasal polyps. It is an allergic response to the presence of topical fungi, often Aspergillus, and is not caused by an invasive infection.

Risk factors

Common risk factors for sinusitis include factors that obstruct normal sinus drainage (eg, allergic rhinitis, nasal polyps, nasogastric or nasotracheal tubes, nasal packing) and immunocompromised states (eg, diabetes, HIV infection). Other factors include prolonged intensive care unit stays, severe burns, cystic fibrosis, and ciliary dyskinesia.

Pathophysiology of Sinusitis

In an upper respiratory infection (URI), the swollen nasal mucous membrane obstructs the ostium of a paranasal sinus, and the oxygen in the sinus is absorbed into the blood vessels of the mucous membrane. The resulting relative negative pressure in the sinus (vacuum sinusitis) is painful. If the vacuum is maintained, a transudate from the mucous membrane develops and fills the sinus; the transudate serves as a medium for bacteria that enter the sinus through the ostium or through a spreading cellulitis or thrombophlebitis in the lamina propria of the mucous membrane. An outpouring of serum and leukocytes to combat the infection results, and painful positive pressure develops in the obstructed sinus. The mucous membrane becomes hyperemic and edematous.


The main complication of sinusitis is local spread of bacterial infection, causing periorbital or orbital cellulitis, cavernous sinus thrombosis, or epidural or brain abscess.

Symptoms and Signs of Sinusitis

Acute and chronic sinusitis cause similar symptoms and signs, including purulent rhinorrhea, pressure and pain in the face, nasal congestion and obstruction, hyposmia, halitosis, and productive cough (especially at night). Often the pain is more severe in acute sinusitis. The area over the affected sinus may be tender, swollen, and erythematous.

  • Maxillary sinusitis causes pain in the maxillary area, toothache, and frontal headache.

  • Frontal sinusitis causes pain in the frontal area and frontal headache.

  • Ethmoid sinusitis causes pain behind and between the eyes, a frontal headache often described as splitting, periorbital cellulitis, and tearing.

  • Sphenoid sinusitis causes less well localized pain referred to the frontal or occipital area.

Malaise may be present. Fever and chills suggest an extension of the infection beyond the sinuses.

The nasal mucous membrane is red and turgescent; yellow or green purulent rhinorrhea may be present. Seropurulent or mucopurulent exudate may be seen in the middle meatus with maxillary, anterior ethmoid, or frontal sinusitis and in the area medial to the middle turbinate with posterior ethmoid or sphenoid sinusitis.

Manifestations of complications include periorbital swelling and redness, proptosis, ophthalmoplegia, confusion or decreased level of consciousness, and severe headache.

Diagnosis of Sinusitis

  • Clinical evaluation

  • Sometimes CT

Sinus infections are usually diagnosed clinically. Imaging is not indicated in acute sinusitis unless there are findings that suggest complications, in which case CT is done. In chronic sinusitis, CT is done more often, and x-rays of the apices of the teeth may be required in chronic maxillary sinusitis to exclude a periapical abscess.

Chronic sinusitis is a common incidental finding in patients who have a head CT for other reasons (eg, patients with headache with or without mild head injury) but is rarely the cause of the patient's symptoms.

Microbial cultures are rarely done because a valid culture requires a sample obtained by sinus endoscopy or sinus puncture; culturing a swab of nasal secretions is inadequate. Cultures are typically done only when empiric treatment fails and in immunocompromised patients and some hospital-acquired causes of sinusitis.


Sinusitis in children can initially be difficult to distinguish from an upper respiratory infection (URI). Bacterial sinusitis is suspected when purulent rhinorrhea persists for > 10 days along with fatigue and cough. Fever is uncommon. Local facial pain or discomfort may be present. Nasal examination discloses purulent drainage and should rule out foreign body.

Diagnosis of acute sinusitis in children is clinical. CT is avoided because of concerns about radiation exposure unless there are signs of orbital or intracranial complications (eg, periorbital swelling, vision loss, diplopia, or ophthalmoplegia), there is chronic sinusitis that has not responded to treatment, or there is concern about rare nasopharyngeal cancer (eg, based on unilateral nasal obstruction, pain, epistaxis, facial swelling, or, particularly concerning, diminished vision). Periorbital edema in a child requires prompt assessment for orbital cellulitis Preseptal and Orbital Cellulitis Preseptal cellulitis (periorbital cellulitis) is infection of the eyelid and surrounding skin anterior to the orbital septum. Orbital cellulitis is infection of the orbital tissues posterior... read more Preseptal and Orbital Cellulitis and possible surgical intervention to prevent visual impairment and intracranial infection.

Treatment of Sinusitis

  • Local measures to enhance drainage (eg, steam, topical vasoconstrictors)

  • Sometimes antibiotics (eg, amoxicillin/clavulanate [amoxicillin/clavulanic acid], doxycycline)

In acute sinusitis, improved drainage and control of infection are the aims of therapy. Steam inhalation; hot, wet towels over the affected sinuses; and hot beverages help alleviate nasal vasoconstriction and promote drainage.

Topical vasoconstrictors, such as phenylephrine 0.25% spray every 3 hours or oxymetazoline every 8 to 12 hours, are effective but should be used for a maximum of 5 days or for a repeating cycle of 3 days on and 3 days off until the sinusitis is resolved. Systemic vasoconstrictors, such as pseudoephedrine 30 mg orally (for adults) every 4 to 6 hours, are less effective and should be avoided in young children.

Saline nasal irrigation may help symptoms slightly but is cumbersome and uncomfortable, and patients require teaching to execute it properly; it may thus be better for patients with recurrent sinusitis, who are more likely to master (and tolerate) the technique.

Corticosteroid nasal sprays can help relieve symptoms but typically take at least 10 days to be effective.

Antibiotic treatment

Although most cases of community-acquired acute sinusitis are viral and resolve spontaneously, previously many patients were given antibiotics because of the difficulty in clinically distinguishing viral from bacterial infection. However, current concerns about creation of antibiotic-resistant organisms have led to a more selective use of antibiotics. The Infectious Diseases Society of America (1 Treatment reference Sinusitis is inflammation of the paranasal sinuses due to viral, bacterial, or fungal infections or allergic reactions. Symptoms include nasal obstruction and congestion, purulent rhinorrhea... read more Treatment reference ) suggests the following characteristics help identify patients who should be started on antibiotics:

  • Mild to moderate sinus symptoms persisting for ≥ 10 days

  • Severe symptoms (eg, fever ≥ 39° C, severe pain) for ≥ 3 to 4 days

  • Worsening sinus symptoms after initially improving from a typical viral URI ("double sickening" or biphasic illness)

Because many causative organisms are resistant to previously used medications, amoxicillin/clavulanate (amoxicillin/clavulanic acid) 875 mg orally every 12 hours (25 mg/kg orally every 12 hours in children) is the current first-line medication. Patients at risk of antibiotic resistance are given a higher dose of 2 g orally every 12 hours (45 mg/kg orally every 12 hours in children). Patients at risk of resistance include those who are under 2 years of age or over 65 years, who have received antibiotics in the previous month, who have been hospitalized within the past 5 days, and those who are immunocompromised.

Adults with penicillin allergy may receive doxycycline or a respiratory fluoroquinolone (eg, levofloxacin, moxifloxacin). Children with penicillin allergy may receive levofloxacin, or clindamycin plus a 3rd-generation oral cephalosporin (cefixime or cefpodoxime).

If there is improvement within 3 to 5 days, the medication is continued. Adults without risk factors for resistance are treated for 5 to 7 days total; other adults are treated for 7 to 10 days. Children are treated for 10 to 14 days. If there is no improvement in 3 to 5 days, a different medication is used. Macrolides, trimethoprim/sulfamethoxazole, and monotherapy with a cephalosporin are no longer recommended because of bacterial resistance. Emergency surgery is needed if there is vision loss or an imminent possibility of vision loss.

Algorithm for use of antibiotics in acute sinusitis

Algorithm for use of antibiotics in acute sinusitis

Adapted from Chow AW, Benninger MS, Brook I, et al: IDSA clinical practice guideline for acute bacterial rhinosinusitis in children and adults. Clinical Infectious Diseases 54 (8):1041–5 (2012).

In exacerbations of chronic sinusitis in children or adults, the same antibiotics are used, but treatment is given for 4 to 6 weeks. The sensitivities of pathogens isolated from the sinus exudate and the patient’s response to treatment guide subsequent therapy.

Sinusitis unresponsive to antibiotic therapy may require surgery (maxillary sinusotomy, ethmoidectomy, or sphenoid sinusotomy) to improve ventilation and drainage and to remove inspissated mucopurulent material, epithelial debris, and hypertrophic mucous membrane. These procedures usually are done intranasally with the aid of an endoscope. Chronic frontal sinusitis may be managed either with osteoplastic obliteration of the frontal sinuses or endoscopically in selected patients. The use of intraoperative computer-aided surgery to localize disease and prevent injury to surrounding contiguous structures (such as the eye and brain) has become common. Nasal obstruction that is contributing to poor drainage may also require surgery.

Treatment reference

  • 1. Chow AW, Benninger MS, Brook I, et al: IDSA clinical practice guideline for acute bacterial rhinosinusitis in children and adults. Clin Infect Dis 54(8):e72-e112, 2012. doi:10.1093/cid/cir1043

Key Points

  • Most acute sinusitis in immunocompetent patients is viral.

  • Immunocompromised patients are at greater risk of aggressive fungal or bacterial infection.

  • Diagnosis is clinical; CT and cultures (obtained endoscopically or through sinus puncture) are done mainly for chronic, refractory, or atypical cases.

  • Antibiotics may be withheld pending a trial of symptomatic treatment, the duration of which depends on the severity and timing of symptoms.

  • The first-line antibiotic is amoxicillin/clavulanate, with doxycycline or respiratory fluoroquinolones as alternatives.

More Information

Invasive Sinusitis in Immunocompromised Patients

Aggressive and even fatal fungal or bacterial sinusitis can occur in patients who are immunocompromised because of poorly controlled diabetes, neutropenia, or HIV infection.


Mucormycosis Mucormycosis Mucormycosis refers to infection caused by diverse fungal organisms in the order Mucorales, including those in the genera Rhizopus, Rhizomucor, and Mucor. Symptoms of rhinocerebral... read more Mucormycosis (zygomycosis, also sometimes called phycomycosis) is a mycosis due to fungi of the order Mucorales, including species of Mucor, Absidia, and Rhizopus. This mycosis may develop in patients with poorly controlled diabetes. It is characterized by black, devitalized tissue in the nasal cavity and neurologic signs secondary to retrograde thromboarteritis in the carotid arterial system.

Diagnosis is based on histopathologic demonstration of mycelia in the avascularized tissue. Prompt biopsy of intranasal tissue for histology and culture is warranted.

Treatment requires control of the underlying condition (such as reversal of ketoacidosis in diabetes), surgical debridement of necrotic tissue, and IV amphotericin B therapy.

Aspergillosis and candidiasis

Aggressive paranasal sinus surgery and IV amphotericin B therapy are used to control these often-fatal infections. If mucormycosis is excluded, voriconazole, with or without an echinocandin (eg, caspofungin, micafungin, anidulafungin), can be used instead of amphotericin.

Drugs Mentioned In This Article

Drug Name Select Trade
Acticlate, Adoxa, Adoxa Pak, Avidoxy, Doryx, Doxal, Doxy 100, LYMEPAK, Mondoxyne NL, Monodox, Morgidox 1x, Morgidox 2x , Okebo, Oracea, Oraxyl, Periostat, TARGADOX, Vibramycin, Vibra-Tabs
Amoclan , Augmentin, Augmentin ES, Augmentin XR
4-Way Nasal, Ah-Chew D, AK-Dilate, Anu-Med, Biorphen, Formulation R , Foster & Thrive Nasal Decongestion, Gilchew IR, Hemorrhoidal , Little Remedies for Noses, Lusonal, Mydfrin, Nasop, Nasop 12, Neofrin, Neo-Synephrine, Neo-Synephrine Cold + Allergy, Neo-Synephrine Extra Strength, Neo-Synephrine Mild, Ocu-Phrin, PediaCare Children's Decongestant, PediaCare Decongestant, PediaCare Infants' Decongestant, Sinex Nasal, Sudafed PE, Sudafed PE Children's Nasal Decongestant , Sudafed PE Congestion, Sudafed PE Sinus Congestion, Sudogest PE, Vazculep
12 Hour Nasal , Afrin, Afrin Extra Moisturizing, Afrin Nasal Sinus, Afrin No Drip Severe Congestion, Dristan, Duration, Genasal , Mucinex Children's Stuffy Nose, Mucinex Full Force, Mucinex Moisture Smart, Mucinex Sinus-Max, Mucinex Sinus-Max Sinus & Allergy, NASAL Decongestant, Nasal Relief , Neo-Synephrine 12-Hour, Neo-Synephrine Severe Sinus Congestion, Nostrilla Fast Relief, Reliable-1 12 hour Decongestant, Rhinase D, RHOFADE, Sinex 12-Hour, Sudafed OM Sinus Cold Moisturizing, Sudafed OM Sinus Congestion Moisturizing, Upneeq, Vicks Qlearquil Decongestant, Vicks Sinex, Vicks Sinex Severe, Visine L.R., Zicam Extreme Congestion Relief, Zicam Intense Sinus
Contac Cold 12 Hour, Dimetapp Decongestant, Drixoral, ElixSure Cold, ElixSure Congestion, Entex, Genaphed , KidKare , Myfedrine, NASAL Decongestant, Nasofed, Nexafed, PediaCare Infants' Decongestant, Pseudo-Time, Silfedrine, Sudafed, Sudafed 12 Hour, Sudafed 24 Hour, Sudafed Children's Nasal Decongestant, Sudafed Congestion, Sudafed Sinus Congestion, Sudogest, Sudogest 12 Hour, Sudogest Children's , Tylenol Children's Simply Stuffy, Zephrex-D
Iquix, Levaquin, Levaquin Leva-Pak, Quixin
Avelox, Avelox ABC Pack, Avelox I.V., MOXEZA, Vigamox
Cleocin, Cleocin Ovules, Cleocin Pediatric, Cleocin T, CLIN, Clindacin ETZ, Clindacin-P, Clinda-Derm , Clindagel, ClindaMax, ClindaReach, Clindesse, Clindets, Evoclin, PledgaClin, XACIATO
Vantin, Vantin Powder
Amphocin, Fungizone
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!