Merck Manual

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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 sinuses, most commonly caused by a viral or bacterial infection or by an allergy.

  • Some of the most common symptoms of sinusitis are pain, tenderness, nasal congestion, and headache.

  • The diagnosis is based on symptoms, but sometimes a computed tomography scan or other imaging tests are needed.

  • Antibiotics can eliminate an underlying bacterial infection.

The Sinuses

Sinusitis is one of the most common medical conditions. Sinusitis may occur in any of the four groups of sinuses: maxillary, ethmoid, frontal, or sphenoid. Sinusitis nearly always occurs in conjunction with inflammation of the nasal passages (rhinitis Rhinitis Rhinitis is inflammation and swelling of the mucous membrane of the nose, characterized by a runny nose and stuffiness and usually caused by the common cold or a seasonal allergy. Colds and... read more Rhinitis ), and some doctors refer to the disorder as rhinosinusitis. It may be acute (short-lived) or chronic (long-standing).

Acute sinusitis

Sinusitis is defined as acute if it is totally resolved in less than 30 days. In people who have a normally functioning immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more , acute sinusitis is usually caused by a viral infection.

Sometimes acute sinusitis is caused by bacteria. Infection often develops after something blocks the openings to the sinuses. Such blockage commonly results from a viral infection of the upper airways, such as the common cold Common Cold The common cold is a viral infection of the lining of the nose, sinuses, and throat. Many different viruses cause colds. Usually, colds are spread when a person's hands come in contact with... read more . During a cold, the swollen mucous membranes of the nasal cavity tend to block the openings of the sinuses. Air in the sinuses is absorbed into the bloodstream, and the pressure inside the sinuses decreases, causing pain and drawing fluid into the sinuses. This fluid is a breeding ground for bacteria. White blood cells and more fluid enter the sinuses to fight the bacteria. This influx increases the pressure and causes more pain.

Allergies Seasonal Allergies Seasonal allergies result from exposure to airborne substances (such as pollens) that appear only during certain times of the year. Seasonal allergies cause itchy skin, a runny nose, sneezing... read more Seasonal Allergies also cause mucous membrane swelling, which blocks the openings to the sinuses. Additionally, people with a deviated septum are more prone to blocked sinuses.

Locating the Sinuses

The sinuses are hollow cavities in the bones around the nose. The two frontal sinuses are located just above the eyebrows. The two maxillary sinuses are located in the cheekbones. The two groups of ethmoid sinuses are located on either side of the nasal cavity. The two sphenoid sinuses (not shown) are located behind the ethmoid sinuses.

Locating the Sinuses

Chronic sinusitis

Sinusitis is defined as chronic if it has been ongoing for more than 90 days. Doctors do not understand exactly what causes chronic sinusitis, but it involves factors that cause chronic inflammation. Factors include chronic allergies Seasonal Allergies Seasonal allergies result from exposure to airborne substances (such as pollens) that appear only during certain times of the year. Seasonal allergies cause itchy skin, a runny nose, sneezing... read more Seasonal Allergies , nasal polyps Nasal Polyps Nasal polyps are fleshy outgrowths of the mucous membrane of the nose. Nasal polyps are more likely to develop in people who have allergies or asthma. Some of the symptoms caused by polyps are... read more Nasal Polyps , and exposure to environmental irritants (such as airborne pollution and tobacco smoke). Often the person has a family history, and a genetic predisposition seems to be a factor. Sometimes the person has a bacterial Overview of Bacteria Bacteria are microscopic, single-celled organisms. They are among the earliest known life forms on earth. There are thousands of different kinds of bacteria, and they live in every conceivable... read more or fungal infection Overview of Fungal Infections Fungi are living organisms, but they are not plants or animals. All living things are divided into categories called kingdoms, and fungi have their own kingdom. Some fungi cause infections in... read more , in which case the inflammation is much worse. Occasionally, chronic sinusitis of the maxillary sinus results when an upper tooth abscess spreads into the sinus above.

Sinusitis may also be subacute (lasting from 30 to 90 days) or recurrent (4 or more episodes of acute sinusitis per year).

Symptoms of Sinusitis

Acute and chronic sinusitis cause similar symptoms, including

  • Yellow or green pus discharged from the nose

  • Headache

  • Pressure and pain in the face

  • Congestion and blockage in the nose

  • Tenderness (pain when touched) and swelling over the affected sinus

  • Reduced ability to smell (hyposmia)

  • Bad breath (halitosis)

  • A productive cough (especially at night)

Some symptoms suggest which sinus is infected:

  • Maxillary sinusitis causes pain over the cheeks just below the eyes, toothache, and headache.

  • Frontal sinusitis causes headache over the forehead.

  • Ethmoid sinusitis causes pain behind and between the eyes, tearing, and headache (often described as splitting) over the forehead.

  • Sphenoid sinusitis causes pain that does not occur in well-defined areas and may be felt in the front or back of the head.

A person also may feel generally ill (malaise). Fever and chills also can occur, but their presence may suggest that the infection has spread beyond the sinuses. Often the pain is more severe in acute sinusitis. Sometimes headache and facial pain increase when lying down or bending forward.

Complications of sinusitis

The main complication of sinusitis is spread of a bacterial infection. An infection may spread to the tissues around the eye (see Introduction to Eye Socket Disorders Introduction to Eye Socket Disorders The eye sockets (orbits) are bony cavities that contain and protect the eyes and their supporting structures (see figures An Inside Look at the Eye and Structures That Protect the Eye). Disorders... read more ) and cause changes in vision or swelling around the eye.

Less commonly, the infection spreads to involve the eye itself, causing eye pain and disturbing vision.

Less often, an infection can spread to tissues around the brain (meningitis Meningitis ) and cause severe headache and confusion. People with sinusitis who develop such symptoms should be evaluated by a doctor as soon as possible.

Diagnosis of Sinusitis

  • A doctor's evaluation

  • Sometimes computed tomography

A doctor bases the diagnosis on the typical symptoms. A computed tomography Computed Tomography (CT) Computed tomography (CT) is a type of medical imaging that combines a series of x-rays to create cross-sectional, detailed images of internal structures. In computed tomography (CT), which used... read more Computed Tomography (CT) (CT) scan is able to determine the extent and severity of sinusitis but is done mainly when people have symptoms of complications (such as a red, bulging eye) or when people have chronic sinusitis. If a person has maxillary sinusitis, the teeth may be x-rayed X-Rays X-rays are a type of medical imaging that use very low-dose radiation waves to take pictures of bones and soft tissues. X-rays may be used alone (conventional x-ray imaging) or combined with... read more to check for a tooth abscess. Sometimes a doctor passes a thin viewing scope (endoscope) into the nose to inspect the sinus openings and to obtain samples of fluid for culture. This procedure, which requires a local anesthetic (to numb the area), can be done in the doctor’s office.

Sometimes findings of chronic sinusitis are incidentally found on a head CT done for other reasons (for example, for people who go to an emergency department with a headache or mild head injury).

Sinusitis in children is suspected when a pus-filled discharge from the nose persists for more than 10 days along with extreme tiredness (fatigue) and cough. Pain or discomfort in the face may be present. Fever is uncommon. When examining the nose, a doctor sees pus-filled drainage. A CT scan can confirm the diagnosis but, because of concerns about radiation exposure, is usually done only in children with chronic sinusitis that does not resolve with antibiotic treatment or with signs of complications.

Treatment of Sinusitis

  • Treatment to improve sinus drainage

  • Medicated nasal sprays

  • Sometimes antibiotics

  • When antibiotics are not effective, surgery

Treatment of acute sinusitis is aimed at improving sinus drainage and curing the infection. Steam inhalation; hot, wet towels over the affected sinuses; and hot beverages may help relieve the swollen membranes and promote drainage. Flushing a saltwater solution through the nose (nasal irrigation) or using a salt-water spray also can help symptoms.

Nasal sprays, such as phenylephrine or oxymetazoline, which cause swollen membranes to shrink, can be used for a limited time. Similar medications, such as pseudoephedrine, taken by mouth are not as effective. Corticosteroid nasal sprays also can help relieve symptoms but take at least 10 days to work.


For acute sinusitis that is severe (3 or more days of symptoms such as fever of 102.2º F [39º C] or higher and severe pain) or persistent (for 10 or more days), antibiotics such as amoxicillin/clavulanate or doxycycline are given.

People who have chronic sinusitis take the same antibiotics but for a longer period of time, typically 4 to 6 weeks.

When antibiotics are not effective, surgery may be performed either to wash out the sinus and obtain material for culture or to improve sinus drainage, which allows the inflammation to resolve. Nasal obstruction that interferes with drainage may also require surgery.

Fungal Sinus Infections

A variety of fungi that are normally found throughout the environment can be present in the nose and sinuses of most healthy people. In certain situations, however, fungi can cause significant nasal and sinus inflammation.

Fungus balls

Fungus balls are overgrowths of Aspergillus fungi in otherwise healthy people.

Symptoms include sinus pain, pressure, nasal congestion, and drainage of fluids.

Surgery is needed to open the affected sinus and remove the fungal debris.

Invasive fungal sinusitis

Symptoms include pain, fever, and discharge of pus from the nose. The fungus may spread to the eye socket, causing a bulging of the affected eye (proptosis Bulging Eyes Bulging or protruding of one or both eyes is called proptosis or exophthalmos. Exophthalmos is usually used when describing bulging eyes caused by Graves disease, a disorder causing overactivity... read more Bulging Eyes ) and blindness.

A doctor bases the diagnosis on the results of a biopsy (removal of a tissue sample for identification under a microscope).

Treatment is with surgery and antifungal medications given by vein. Doctors also must control the underlying disease and stimulate a weakened immune system because this invasive sinus infection can cause death.

Allergic fungal sinusitis

The polyps obstruct the nose and the openings to the sinuses and cause chronic inflammation.

Surgery is typically required to open up the sinuses and to remove the fungal debris. Long-term treatment is also required with corticosteroids, antibiotics, and, sometimes, antifungal medications applied directly to the area or taken by mouth. These medications reduce the inflammation and eliminate the fungus. However, even after long-term treatment, the disorder is very likely to recur.

Drugs Mentioned In This Article

Generic Name Select Brand Names
4-Way Nasal, Ah-Chew D, AK-Dilate, Anu-Med, Biorphen, Formulation R , Foster & Thrive Nasal Decongestion, Gilchew IR, Hemorrhoidal , IMMPHENTIV, 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
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
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