What Causes Sinus Infections?

A sinus infection, or sinusitis, is when you have an inflamed or stuffy nose or fluid buildup in your sinuses. The fluid build-up provides an environment where germs associated with viruses or bacteria can grow. There are several causes of sinus infections, with the most common cause being the common cold. You may have a sinus infection from other causes, including a benign growth in the sinuses called nasal polyps or allergies.

In this article, you’ll learn more about the common causes of sinus infections so you can narrow down the potential cause of your sinus infection as well as treatments, risk factors and prevention.

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The Main Causes of Sinus Infections

The three main causes of sinus infections are:

  • Infection, typically caused by viruses or bacteria
  • Nasal polyps (benign growths that contain mucus)
  • Allergies such as seasonal allergies or allergies to environmental triggers

A Common Cause of Acute Sinusitis

The common cold is the most common cause for acute sinusitis or sudden sinus infection. It usually is caused by a viral infection, although bacteria and fungi can also lead to acute sinus infections.

How Long Does Acute Sinusitis Last?

Acute sinus infections can last anywhere from three to eight weeks.

The risk for sudden sinus infection caused by bacteria or fungi is greater in people with compromised immune systems. 

Common Causes of Chronic Sinusitis

Common causes of chronic sinusitis include:

  • Allergies to pollen, dust, mold, or fungi spores
  • Nasal polyps
  • Tumors
  • Fractures

Chronic sinusitis in adults is most often caused by nasal swelling and inflammation associated with allergies. These allergies trigger the release of histamines to the affected area, which cause nasal passageway inflammation. Structural differences, including polyps, fractures, or a narrowing within the nasal cavity, can also promote chronic infection. This is because when the nasal passage is blocked in any way, fluid buildup can occur and prevent proper drainage.

What Makes a Sinus Infection Chronic

Any sinus infection lasting longer than eight weeks is considered chronic sinusitis.

People who live with asthma, cystic fibrosis, and immune system challenges have a greater chance of developing chronic sinusitis.

Sinus Infection Symptoms

The most common symptoms of sinus infection include:

  • Runny nose or stuffy nose
  • Facial pain or pressure
  • Headache
  • Mucus dripping down the throat (postnasal drip)
  • Greenish nasal discharge
  • Enlarged lymph nodes
  • Sore throat 
  • Cough
  • Bad breath despite brushing teeth

These symptoms can last around 10 days, but you should be seeing improvements as the days pass.

Sinus Infection Treatment

A sinus infection may or may not require antibiotic treatment. Most sinus infections will resolve without antibiotic treatment. Your healthcare provider can help determine whether antibiotics are necessary. Usually, taking unnecessary antibiotics won't help your condition, and overuse of antibiotics can result in unwanted side effects, including antibiotic resistance (when germs develop the ability to fight off the drugs used to kill them).

In some cases, your healthcare provider will suggest a method called watchful waiting or delayed antibiotic prescribing, as follows:

  • Watchful waiting is when your healthcare provider monitors symptoms for two or three days before deciding whether to prescribe antibiotics. Two or three days is enough time to see if your immune system will fight the infection independently.
  • Delayed prescribing is when your healthcare provider writes the antibiotic prescription but asks you to wait two to three days before filling it to see if it's necessary or if your symptoms are improving.

Methods of at-home treatment include:

  • Nasal decongestant sprays: These sprays can taken up to four days. They help reduce swelling and promote free-flowing drainage from the nasal cavity.
  • Antihistamines: These medications can help reduce inflammation caused by allergy-induced infection.
  • Combination medications: These include both decongestant medication and antihistamines. These should only be taken for a sinus infection after consultation with a healthcare provider or allergist.
  • Topical prescription nasal corticosteroid sprays: These drugs help reduce inflammation and swelling but can also be effective in reducing the size of nasal polyps if they are obstructing airflow.

Home Remedies to Help Sinus Infections

There are ways of feeling better when you have a sinus infection. A common home remedy for sinus infection is using a nasal saline rinse. Saline rinses are a sanitary way to help clear the nasal passageway.

Other at-home remedies for sinus infection relief include:

  • Using a warm compress over the nose and forehead area to help relieve pressure and promote drainage
  • Breathing in clean steam from hot water
  • Using a humidifier to keep at-home air moist and prevent nasal passage dryness
  • Drinking plenty of water to help loosen mucus
  • Sleeping with your head elevated

What Are the Risk Factors for Sinus Infections?

Risk factors play a role in who will experience sinus infections, and how often. Common risk factors for sinus infections include:

  • A previous, recent cold
  • Seasonal allergies
  • Exposure to smoke, including secondhand smoke
  • Structural differences including being born with a narrow nasal passageway or developing a nasal polyp
  • Compromised immune system
  • Taking medications or drugs that weaken the immune system's defenses

Is Sinus Surgery Necessary to Reduce Risk?

People who are born with narrow nasal passageways may be advised to seek surgical remedy if they have chronic sinus infections. This is an effective way of reducing this common risk factor for sinus infection.

Can Sinusitis Be Prevented?

There are several ways you can help protect yourself from having a sinus infection. These include general methods of preventing infection or spreading illness that can help keep yourself and others healthy. Prevention efforts include:

  • Wash your hands thoroughly and frequently.
  • Stay up-to-date on vaccines including the flu vaccine but also the pneumococcal vaccine.
  • Avoid smoking or exposure to secondhand smoke.
  • Avoid close contact with someone with a sinus infection or upper respiratory infection.
  • Consider getting a humidifier to help keep the household air moist (be sure to stay on top of cleaning your humidifier).

When to Contact a Healthcare Provider

If you’re experiencing repeat infections or if you have multiple sinus infections in a single year, it’s time to consider seeing your healthcare provider to discuss the underlying reason.

Signs of severe and concerning symptoms associated with sinus infection are also cause for contacting your healthcare provider. These signs include:

This is not a full list of severe or concerning symptoms. If you are experiencing other concerning symptoms, contact your healthcare provider to learn of the next steps so you can start feeling well.

When to Seek ER Treatment

If you have a child under the age of three months with a fever of 100.4 degrees F (38 degrees C) or higher, seek immediate medical care from a healthcare provider. In adults, the signs it's time to go to the emergency room for immediate treatment include:

  • High fever
  • Confusion
  • Vision changes
  • Seizures
  • Stiff neck
  • Difficulty speaking, swallowing, or breathing
  • Red, swollen, or painful eye
  • Swelling of face or mouth

Summary

A sinus infection is when your nasal cavity becomes inflamed, and fluid builds up, allowing germs to grow and cause infection. Causes of sinus infections include viruses, bacteria, allergies, and structural differences in the nasal passageway that can cause obstructions and promote fluid buildup. Treatment for sinus infections includes antibiotic treatment, medications, and at-home remedies for symptom relief.

Consult with a healthcare provider to determine the underlying cause and best treatment methods for your sinus infection. See a healthcare provider if symptoms last longer than 10 days, persist despite treatment, or have a fever lasting more than three to four days.

4 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.
  1. Centers for Disease Control and Prevention. Sinus infection (sinusitis).

  2. Harvard Health Publishing. Chronic sinusitis (in adults).

  3. American College of Allergy, Asthma, and Immunology. Sinus infection: Causes, symptoms, and treatment.

  4. Harvard Health Publishing. Sinusitis.

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By Michelle Pugle
Michelle Pugle, MA, MHFA is a freelance health writer as seen in Healthline, Health, Everyday Health, Psych Central, and Verywell.