Sinus Infections and What Causes Them

A sinus infection is inflammation of the sinuses, which are the air spaces around your nose, eyes, cheeks, and forehead. It is also called sinusitis. When the sinuses are inflamed, drainage is blocked and the sinuses fill with mucus. This can cause a sensation of pain and pressure along with a stuffy nose and sometimes a fever.

Acute sinus infections often start with 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. 

Types

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

• Acute sinusitis: Symptoms are present for less than four weeks.
• Subacute sinusitis: Symptoms are present for more than four but less than 12 weeks.
• Chronic sinusitis: Symptoms are present for 12 weeks or more. 
  
• Recurrent sinusitis: When you have four or more sinus infections in a year.

Symptoms

The sinuses are air spaces surrounded by bone located near your eyes, nose, cheeks, and forehead. The sinuses are lined with mucous membranes that normally produce mucus.

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.

Acute and Subacute

Symptoms of 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.

Chronic

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 (where a mass of fungi grows in what's called a fungal ball), it will cause only a few symptoms. This may 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.

Recurrent Sinusitis

Recurrent sinus infections occur when you experience sinus infections multiple times over a period of one year. These sinus infections have the usual symptoms of acute sinusitis, and they resolve between episodes.

Complications

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
• Vision changes
  

Causes

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)

Other causes of chronic or recurrent sinus infections include:

• Structural abnormalities within the nasal passages and sinuses, such as a perforated 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, which 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.

Diagnosis

Diagnosis of sinus infection is 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.

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.

Treatment

Sinus infection treatment depends on the cause. The typical acute/subacute viral sinus infection will go away on its own in 10 days or less.

Self-Care

Most people only need symptomatic treatment for comfort. Some of the things you can do to reduce discomfort during a sinus infection include the following:

• Drink plenty of fluids to help loosen mucus.
• Get plenty of rest.
• Use a humidifier in your home.
• Apply a warm compress to your face.
• Inhale steam in a shower or from a hot bowl of water.

Medication

If your infection is chronic and/or bacterial, your healthcare provider may prescribe medication.

• Saline nasal spray or irrigation: 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.
• Antibiotics: The primary treatment for bacterial sinus infections is a 10- to 14-day course of antibiotics (typically amoxicillin or amoxicillin-clavulanate). If you have a chronic sinus infection, you may need antibiotics for four to six weeks.
• Steroid nasal spray: 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.
• Decongestants: Topical or oral decongestants can help reduce pain and pressure.
• Over-the-counter pain medication: Tylenol (acetaminophen) and Advil (ibuprofen) can help relieve pain during a sinus infection.

Surgery

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.

Prevention

You can't always prevent sinus infections, but there are some things you can do to stay healthy:

• Wash your hands often.
• Get recommended vaccines such as an annual flu and COVID-19 shot.
• Avoid contact with people who have respiratory infections.
• Avoid secondhand smoke and quit if you are a smoker.
• Use a humidifier in your home.
  

Summary

A sinus infection is an infection of the sinuses, typically caused by a virus or bacteria. It can cause pain and swelling, a stuffy nose, and sometimes fever.

Most sinus infections will resolve on their own without treatment. Self-care can include over-the-counter pain relievers, decongestants, fluids, rest, using a humidifier, and applying a warm compress to your face. If your symptoms persist for more than 10 days, speak with your healthcare provider.