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Sinusitis is an inflammation of the paranasal sinuses. The full medical term for sinusitis is "rhinosinusitis" ("rhino-" meaning "nose"), because it affects the mucous membranes lining both the nose and the sinuses.

The paranasal sinuses are part of the upper airways, and are connected to the nasal cavity. They are made up of several cavities in the skull found from the forehead down to the teeth of the upper jaw. Depending on where they are, these cavities are known as the frontal sinuses, the sphenoid sinus, the ethmoid cells and the maxillary sinuses. The paranasal sinuses are lined with mucous membranes that have tiny hairs on them (ciliated epithelium). These mucous membranes produce a secretion that runs down through the nose and throat.

Sinusitis can be acute or chronic: The acute form may appear several times a year, but it always goes away within several weeks at the latest. In chronic sinusitis, the mucous membranes lining the paranasal sinuses are inflamed for a longer period of time. Sinusitis is commonly considered to be chronic if the symptoms continue for more than three months.


Sinusitis often has the following typical symptoms:

Stuffy nose





A build-up of pus

If you have sinusitis, your nasal passages will become blocked due to the swelling and build-up of fluid. This makes it more difficult to breathe through the nose, which feels stuffy. A yellowish or greenish discharge is a sign of the presence of germs.

Sinusitis often causes pain in the forehead, the jaw and around the eyes and – less commonly – toothache. The pain and stuffy feeling usually get worse when you lean forward, for example when getting up out of bed. Your sense of smell is often affected, and you may lose it completely.


Common causes of chronic sinusitis include:

Nasal polyps. These tissue growths can block the nasal passages or sinuses.

Deviated nasal septum. A crooked septum — the wall between the nostrils — may restrict or block sinus passages, making the symptoms of sinusitis worse.

Other medical conditions. The complications of conditions such as cystic fibrosis, HIV and other immune system-related diseases can lead to nasal blockage.

Respiratory tract infections. Infections in your respiratory tract — most commonly colds — can inflame and thicken your sinus membranes and block mucus drainage. These infections can be caused by viruses or bacteria.

Allergies such as hay fever. Inflammation that occurs with allergies can block your sinuses.

Risk factors

Sinusitis often occurs when something, such as mucus, blocks the openings of your sinuses.

Anyone can develop sinusitis or a sinus infection. However, certain health conditions and risk factors can increase your chances.

Possible contributors to sinusitis include:

structural issues affecting the nose, such as:

a deviated septum, which occurs when the wall of tissue that runs between the left and right nostrils is uneven

a nasal bone spur, or growth

nasal polyps, which are usually noncancerous

weakened immune system

a history of allergies

colds and other upper respiratory tract infections, which can be caused by viruses, bacteria, or fungi

cystic fibrosis, which causes thick mucus to build up in your lungs and other mucous membrane linings

mold exposure

tobacco smoking

dental infection

airplane travel, which can expose you to a high concentration of germs

Sometimes, a cold, allergens, or bacteria can cause too much mucus to form. This mucus buildup can become thick and encourage bacteria and other germs to build up in your sinus cavity, eventually leading to a sinus infection.

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Chronic sinusitis. Acute sinusitis may be a flare-up of a long-term problem known as chronic sinusitis. ...

Meningitis. This infection causes inflammation of the membranes and fluid surrounding your brain and spinal cord.

Other infections. ...

Vision problems.


Because sinusitis can develop after a cold, the flu, or an allergic reaction, following a health-promoting lifestyle and reducing your exposure to germs and allergens can help prevent this inflammation.

To reduce your risk, you can:

Get a flu shot every year.

Eat nutritious foods, such as fruits and vegetables.

Wash your hands regularly.

Limit your exposure to smoke, chemicals, pollen, and other allergens or irritants.

Take antihistamine medication to treat allergies and colds.

Avoid exposure to people with active respiratory infections, such as a cold or the flu.