What Is a Sinus Infection?

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A sinus infection, also called sinusitis, is an inflammation of the air spaces around your nose and eyes, including the paranasal cavities. When sinus drainage is blocked, the sinuses fill with mucus, and this can cause a sensation of pain and pressure.

Acute sinus infections often start with inflammation from allergies or viral infection (such as a cold) and sometimes develop into a bacterial infection. Chronic sinus infections are usually due to ongoing inflammation. Structural abnormalities in the sinuses can predispose to chronic or recurrent sinusitis. Fungal sinus infections are not as common, but they can affect people who have weakened immune systems.

The Sinuses

The sinuses are air spaces surrounded by bone that are located near your eyes, nose, cheeks, and forehead. They include the frontal, maxillary, sphenoid, and ethmoid sinuses.

The sinuses are lined with mucous membranes that normally produce mucus, a type of fluid that helps trap debris. Microscopic hair-like cilia cells line the membranes and sweep along the mucus, which usually drains into the nasal passages throughout the day.

When the drainage sites for the sinuses are blocked, the sinuses cannot drain, and an infection may develop. The mucus is thickened by inflammatory cells and bacteria during an infection, and it changes from a watery to a thick consistency and changes color from clear to yellow or green.

Sinus Infection Symptoms

Sinus infections can be divided into different categories based on how long the infection has been going on.

With acute sinusitis, symptoms are present for less than four weeks. Subacute sinusitis indicates that symptoms are present for more than four but less than 12 weeks.

Symptoms often associated with acute and subacute sinusitis include:

  • Facial pain and pressure over the involved sinus(es)
  • Nasal congestion
  • Colored nasal discharge
  • A decrease in smell and taste sensations
  • Fever
  • A headache
  • Bad breath/bad taste
  • Fatigue
  • A cough
  • Tooth pain
  • Ear pressure/pain

A viral sinus infection tends to improve without treatment. An acute bacterial sinus infection, on the other hand, is presumed if your symptoms extend past 10 days, if they get worse after getting better, or if they are severe.

An acute invasive fungal infection is a rare type of sinus infection that can affect people who have a severely suppressed immune system. The symptoms begin with fever, cough, nosebleed, and headache. These infections can involve the eye, with symptoms of swelling or vision changes, and they may affect the brain.

Chronic Sinusitis

The symptoms of chronic sinusitis are mild and include:

  • Nasal congestion
  • Postnasal drip or a runny nose with mucus
  • Pain or pressure in the face
  • Decreased sense of smell and taste
  • Chronic cough (in children)

If the chronic sinusitis is due to noninvasive fungal sinusitis (fungal ball), it will cause only a few symptoms, which may only include a feeling of fullness, sinus pressure, and some discharge. Chronic invasive fungal sinusitis mostly affects people who are immunocompromised. It causes the usual symptoms of chronic sinusitis for a long time, but it can cause serious symptoms of decreased vision and an inability to move the eye as the infection progresses.

You are diagnosed with chronic sinusitis when your symptoms are present for 12 weeks or more. 

Recurrent Sinusitis

These sinus infections have the usual symptoms of acute sinusitis, and they resolve between episodes.

You're considered to have recurrent sinusitis when you have four or more sinus infections in a year.


Complications of sinus infections are uncommon, but it is possible for the infection to spread to the tissues around the eyes, skull, or brain. See your healthcare provider immediately if you have symptoms such as high fever, swelling around the eyes or forehead, confusion, severe headache, or vision changes.


Allergic rhinitis and upper respiratory tract infections are risk factors for acute and chronic sinusitis. Other conditions that can increase the chance of developing sinus infections include gastroesophageal reflux disease (GERD) and non-allergic rhinitis. You may be more prone to either form of sinusitis if you have structural abnormalities that inhibit sinus drainage.

Problems with low immune function are the biggest risk factor for fungal sinusitis, but they also increase the risk of various types of viral and bacterial infections. Immunodeficiencies can occur as a result of a genetic problem (such as cystic fibrosis), infection (such as HIV/AIDS), or diseases that affect antibody levels (such as multiple myeloma). Diabetes can also be a risk factor for fungal sinus infections.

Acute or Subacute Sinus Infections

An acute or subacute sinus infection starts with inflammation of the nasal passages, which can occur due to an irritant, allergy, or infection, such as the common cold. The resulting blockage of sinus drainage leads to the development of the infection.

Chronic or Recurrent Sinus Infections

Chronic or recurrent sinusitis is usually caused by ongoing inflammation rather than infection. It can develop due to factors such as allergic rhinitis, fungal allergies, aspirin-exacerbated respiratory disease (AERD), exposure to irritants (such as cigarette smoke), or repeated viral infections.

Other causes of chronic or recurrent sinus infections include structural abnormalities within the nasal passages and sinuses, such as a deviated septum (the structure that divides the nasal passage into two sides); enlarged adenoids; enlarged turbinates (structures that warm the air in your nose); nasal polyps; and other bony abnormalities that may prevent the sinuses from draining.

Fungal Sinus Infections

A fungal sinus infection can develop either as a non-invasive fungal ball or as an invasive fungal infection that can damage nearby structures. A fungal ball may develop when dead cells and debris from inflammation or an injury accumulate in the sinus and a fungus that's normally present in the air begins to grow. This can cause further irritation and inflammation.

These organisms are present in the air, but don't usually invade the body—they are only able to grow when the body's immune defenses are very low.

sinusitis diagnosis
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A sinus infection is diagnosed based on your symptoms and a physical examination by your healthcare provider. No other tests are usually needed for the diagnosis of an uncomplicated acute or subacute sinus infection. If allergies are suspected, you may be referred for allergy testing. If you have recurrent or chronic sinusitis, your healthcare provider may order CT imaging to look for the underlying cause.

Microscopic examination and culture of the aspirate from the sinuses can help diagnose fungal or resistant bacterial infections.

In severe cases of sinusitis, especially those that do not respond to the usual medical treatments, you may be referred to an ear-nose-throat (ENT) specialist or otolaryngologist.


The treatment of sinus infection depends on the cause. The typical acute/subacute viral sinus infection will resolve itself in 10 days or less. You or your child will only need symptomatic treatment for comfort. Saline nasal spray or, for adults, nasal saline irrigation, can help remove the mucus from the nasal passages and sinuses. These remedies can also be helpful for adults with recurrent or chronic sinusitis.

The primary treatment for bacterial sinus infections is a 10- to 14-day course of antibiotics (typically amoxicillin or amoxicillin-clavulanate).

Chronic Infections

Chronic sinus infection treatment often includes a nasal steroid spray. In cases of severe inflammation, the use of oral steroids such as prednisone for three to 10 days is often recommended.

Other helpful medications include topical or oral decongestants. Antibiotics may or may not be prescribed depending on whether a bacterial infection is present. If so, the therapy may continue for four to six weeks.


Some people require surgery if recurrent sinus infections are caused by severe structural problems or nasal polyps. Endoscopic surgery may also be needed for fungal sinus infections.

A Word From Verywell

While a sinus infection is usually self-limited, it can be quite debilitating while you have it, often distracting you from just about everything but the discomfort it causes. Remember that relief is typically days away. While you wait, you can take over-the-counter pain relievers, drink lots of fluids, get plenty of rest, use a humidifier, and apply a warm compress to your face for comfort. And if your symptoms persist for more than 10 days, be sure to speak with your healthcare provider again.

22 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
Daniel More, MD

By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and formerly practiced at Central Coast Allergy and Asthma in Salinas, California.