Sinus infection, also referred to as sinusitis or rhinosinusitis, is an inflammation of the tissue lining the sinus cavities.

Sinusitis is one of the most commonly diagnosed diseases in the United States, affecting an estimated 16 percent of the adult population annually.

The sinuses are a connected system of air-filled cavities located in the skull.

Inflammation of the sinuses is caused by a virus, bacteria, fungus, or as a result of allergies. The inflammation prevents the sinuses from draining normally, leading to a build up of mucus and secondary infection.

The main symptoms of sinus infection are nasal obstruction, discolored nasal discharge, and facial pain or pressure that has been present for 7 days or more.

Fast facts on sinusitis

Here are some key points about sinusitis.

  • Normally, the sinuses are empty except for a thin layer of mucus
  • When the sinuses become inflamed and swollen, they are no longer able to drain mucus, resulting in a build-up
  • The overwhelming majority of cases of sinusitis are viral in nature and require symptomatic relief, not antibiotics
  • Only about 0.5-2.0 percent of sinus infections episodes are bacterial
  • Antibiotics are the primary form of medical treatment for acute bacterial sinusitis

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Nasal discharge is one of the main symptoms of sinusitis.

Sinus infections are classed as acute or chronic:

  • acute sinus infection only lasts for a short time and is often part of a cold or allergy
  • chronic sinus infection lasts more than 12 weeks and may reoccur

A sinus infection, whether chronic or acute, normally consists of the following symptoms:

Facial pain or pressure

Pain is a common symptom in sinusitis. A person may feel the pain around their eyes, under their eyes, on their forehead, and around their nose. The roots of the teeth project into the floor of the maxillary sinus, which can cause a person to feel pain in their teeth.

Sinus pain can also feel like a generalized headache. The pain is often described as throbbing, and it may get worse when a person strains or bends down.

Nasal discharge

Nasal discharge is prominent in sinusitis as the mucous membrane of the nose and sinuses are attached. The drainage may be cloudy or colored green or yellow, blood-tinged, thick, and foul-smelling.

This increase in discharge is why people need to blow their nose more often. If the discharge trickles down the throat, it may cause an unpleasant taste in the mouth and an itching sensation at the back of the throat; this is referred to as a post-nasal drip.

Cough and sore throat

The trickle of fluid can irritate the throat (especially over longer periods of time) and produce a cough. When an individual lies down at night, there is an increase in the flow of fluid down the back of the throat, which can make the cough worse.

Post-nasal drip can also cause a person's voice to sound hoarse and potentially produce bad breath and a sore throat.

Nasal congestion

The inflamed sinuses can affect breathing. Because of the swelling of the sinuses and nasal passages, it is more difficult for air to travel past. This can also impact on an individual's sense of smell and taste.

A virus, bacteria, or an allergen can cause sinusitis.

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A runny nose and sore throat may be symptoms of viral sinusitis.

Viral sinusitis

The symptoms of viral sinusitis tend to be cold-like, including runny nose, sore throat, sneezing, nasal congestion, and coughing. Mucus may be clear, or slightly colored.

Antibiotics are not effective against a viral infection. The best treatment is to manage the symptoms by getting as much rest as possible, drinking fluids, using saline nasal sprays, and taking over-the-counter pain relievers and oral decongestants.

Sinusitis caused by a virus typically resolves in 7-10 days.

Bacterial sinusitis

The symptoms of bacterial sinusitis include nasal discharge that may be thick, and green or yellow. The nasal passages are swollen and mucus may be dripping down the back of the throat (post-nasal drip). People may also experience facial pain and pressure.

A person who has a bacterial sinus infection should see a doctor for prescription antibiotics such as amoxicillin. The majority of individuals with acute bacterial sinusitis respond successfully to antibiotics, with symptoms clearing up in 10-14 days.

Allergic sinusitis

Sinusitis due to an allergy can cause inflammation that leads to nasal congestion and swelling of the mucous membranes, which can block normal sinus drainage. Allergic sinusitis often leads to chronic sinusitis. Symptoms can be seasonal, or last all year round, and include:

  • sneezing
  • itchy nose, throat, or eyes
  • nasal congestion
  • postnasal drip
  • runny (clear mucus) nose

Treatment for allergic sinusitis includes antihistamines, avoiding allergic triggers, and, in some cases, allergy shots.

Chronic sinusitis

Chronic sinusitis can cause more subtle symptoms that persist for months. Nasal congestion and post-nasal drainage are the most common symptoms of chronic sinusitis. A cough that is worse at night or on awakening in the morning is common, too. Individuals with nasal polyps more commonly have this type of infection.

Nasal steroid sprays are typically used as a form of treatment; fungus is a likely cause of chronic sinusitis.

Although most cases of sinus infection are uncomplicated, potentially life-threatening complications of acute bacterial sinusitis can occur.

The walls of the sinuses are thin, and the sinuses share blood vessels and lymph drainage pathways with the eyes and parts of the central nervous system.

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Facial pain or pressure is one of the three main symptoms of sinusitis.

Complications of sinus infection include:

Symptoms of these rare complications include:

  • redness or swelling in the eye or eye socket
  • pain with eye movements
  • changes in vision
  • drooping eyelid
  • sensitivity to light
  • swelling of the forehead
  • severe headache
  • onset of fever
  • confusion
  • seizure
  • inability to move neck forward (nuchal rigidity)

Anyone that develops any symptoms that suggest a potential complication of sinusitis must seek immediate medical attention.

The vast majority of sinusitis cases are caused by a virus and clear up on their own in 7-10 days. When symptoms extend beyond 10 days or worsen in severity, people should see their doctor.