What is sinusitis?

What are sinuses?

The sinuses are hollow air filled cavities within the skull bones. There are four pars of sinuses and these are located behind the forehead (a pair), under the cheek bones (a pair), behind the eyes (a pair) and on either side of the bridge of the nose (a pair).

The sinuses are lined with a mucous membrane and function to humidify and warm the inhaled air before they can reach the lungs. The membranes within the sinuses contain tiny hairs called cilia. These move to allow movement of air and mucus within the sinuses and help remove foreign objects or microorganisms.

The sinuses normally produce mucus that is drained into the nose cavity through small channels. These channels also allow the air inhaled through the nose to circulate freely into and out of the sinuses. 1-7

What causes sinusitis?

Sinusitis refers to the inflammation and infection of the lining of these sinuses. The infection may be caused by a virus, bacteria or even fungi.

Inflammation makes the mucous membranes swollen and also blocks the channels that drain the mucus from within the sinuses. This causes accumulation of the fluid and leads to the symptoms of pain over the sinuses. The sinuses behind the cheekbones are most commonly affected.

People who get sinusitis may have medical problems with the cilia lining the sinuses as for example in patients of cystic fibrosis. In addition, colds and even allergies lead to formation of excess mucus and these block the opening of the sinuses.

Those with anatomical defects like a deviated nasal septum, nasal bone spur or formation of nasal polyps also develop a blockage to the channels of the sinuses that predisposes them to develop sinusitis.

Smokers, those with large adenoids, tooth infections, those travelling to high altitudes or scuba diving may also be at risk of sinusitis.

Who does sinusitis affect?

Sinusitis is more common in adults. It rarely occurs in children under the age of five. Acute sinusitis is a very common condition affecting about 15% of the population in Western countries.

In the UK a general practice is expected to encounter about 250 cases of acute sinusitis per 10,000 person-years.

What are the symptoms of sinusitis?

There may be typical symptoms of fever, pain and tenderness over the face particularly over the sinuses. There may be a blocked or runny nose as well. There is a bad breath if there is formation of pus within the sinuses. There may be cough that usually worsens at night. Headache, sore throat and dripping of mucus at the back of the throat (post nasal drip) are other symptoms.

Sinusitis may either be acute, sub-acute or chronic. Acute sinusitis develops quickly over a few days after a bout of cold or flu and never lasts beyond 4 weeks. Those with sub-acute condition may have symptoms lasting between 4 and 12 weeks. If the symptoms persist for over 3 months (12 weeks) sinusitis is said to be chronic. Chronic sinusitis is less common and may last for months or even years.

Diagnosis of sinusitis

This is usually done by doctors who specialize in ear, nose, and throat problems (ENTs). For detection of sinusitis clinical features are used. In addition, anatomical defects like deviated nasal septum, nasal polyps or nasal bone spurs are looked for as these may predispose to a recurrence of sinusitis.

A light is shined through the sinus (transillumination) to look for signs of inflammation. Regular X rays may reveal whitish patches of mucus accumulation within the affected sinuses.

More advanced methods include use of a nasal endoscope or a thin tube with a light and camera on its tip. The tube is inserted within the nose and sinuses to view the insides and detect infection and inflammation.

A CT scan or MRI is suggested to detect the anatomy of the sinuses and also to detect tumors or fungal infections.

Other tests for recurrent sinusitis include allergy testing, blood tests for poor immune functions or HIV AIDS, test for functions of the cilia (Ciliary function tests), sweat chloride tests (for detection of cystic fibrosis) and histology or cell structure of the mucous linings of the nose and sinuses.

Treatment of sinusitis

In most cases over the counter painkillers and decongestants, available at pharmacies, may be used to ease the pain and blocked nose and sinuses.

Warm compress over the sinuses, inhalation of steam, nasal saline sprays, use of the humidifier or the Neti pot to flush the sinuses are other self-care remedies for sinusitis.

Antibiotics are prescribed only if the infection is found to be of a bacterial nature or the sinusitis has become persistent or chronic. Nasal corticosteroid sprays and antihistamines may be prescribed to decrease swelling, especially if there are nasal polyps or allergies.

Surgery to clean and drain the sinuses may also be necessary. Fungal sinusitis usually require surgery.


In nearly two thirds of individuals, sinusitis does not require therapy and clears up on its own. Usual time for clearing up is around two to three weeks.

Further Reading

Last Updated: Mar 15, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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