What is sinusitis (sinus infection)?

Sinusitis¹, or a sinus infection, is caused by viral, bacterial, or fungal infections and causes inflammation or swelling of the tissue that lines the sinuses.

The sinuses² are hollow, connected cavities located in the skull. They are found within the cheeks, behind the forehead and eyebrows, on either side of the nasal bridge, and directly behind the nose.

Sinuses are lined with soft pink tissue, and are usually empty besides a thin layer of mucus. This mucus helps trap particles in the air—including dust and germs—to prevent them from getting inside the body and causing infection.

Normally, mucus flows through the sinuses to the back of the throat with the help of tiny hairs called cilia. Sometimes, however, a buildup of fluid can slow or block the flow of mucus through the sinuses, allowing germs to grow more easily. These germs can cause the sinuses to become inflamed, leading to the infection known as sinusitis.

While viruses are the most common cause of sinusitis, a sinus infection can also be the result of infection from bacteria, allergens, or fungi.

Some common symptoms of sinus infections include nasal inflammation, congestion (which can cause difficulty breathing through your nose) or a runny nose, pain or swelling located around the sinuses, and consistent mucus drainage down the back of the throat (known as postnasal drip). Other less common symptoms include ear pain, aching in the upper jaw or teeth, a cough, sore throat, bad breath, and fatigue.

Acute vs. chronic sinusitis

Sinus infections can be classified in two different ways: acute and chronic.

Acute sinusitis³—or sinusitis with severe and quickly developing symptoms—describes a sinus infection that lasts less than 4 weeks. Most cases of acute sinusitis start with a common cold. Symptoms usually go away between 7–10 days, but they can sometimes lead to the development of a further bacterial infection.

Chronic sinusitis⁴ refers to persistent or recurrent sinus infection. It may be caused by a bacteria or fungus, and is generally diagnosed only after the symptoms of a sinus infection have lasted for more than 12 weeks with medical treatment.

People with allergic rhinitis (seasonal allergies, or “hay fever”) or asthma are more likely than others to suffer from chronic sinus infections because their airways are more susceptible to inflammation.

How common is sinusitis?

Sinusitis is very common⁵: it affects 31 million people in the U.S. annually.

Each year, Americans spend roughly $150 million on prescription medications and $1 billion on over-the-counter medications to treat sinus infections. Sinusitis is also responsible for more than 16 million annual visits to healthcare providers.

Sinus infections can be caused by viruses and bacteria that cause infections like the common cold, the flu, and strep throat.

Sinusitis Symptoms

While sinus infections often resolve themselves, they can be uncomfortable.

Chronic sinusitis and acute sinusitis share many of the same signs and symptoms. Because acute sinusitis is often associated with a cold, however, if you have an acute sinus infection you may also have cold symptoms that are not generally present in sinusitis alone.

The most common symptoms of sinusitis include:

• Postnasal drip (persistent flow of mucus down the throat)
• Discolored nasal discharge (notably greenish in color)
• Nasal stuffiness or congestion
• Pressure or tenderness behind the face (particularly under the eyes or at the bridge of the nose)
• Headaches towards the front of the skull
• Upper jaw or teeth pain
• Cough
• Fatigue
• Fever
• Bad breath

Severe cases of the common cold are often mistaken for sinusitis⁶. Colds and sinus infections share many symptoms, including headache and a runny or stuffy nose. However, while the common cold is caused by viral infections (most commonly the rhinovirus), sinusitis may also be caused by allergens, fungi, or bacteria.

Serious sinusitis symptoms

While sinus infections often go away on their own, they pose a number of risks for causing serious complications. Because part of your sinuses is located close to the brain, the spread of infections in this area can be dangerous and possibly life-threatening.

You should call your healthcare provider if you experience any of the following:

• Symptoms lasting longer than 10–14 days or that worsen after 7 days
• A severe headache that is not alleviated by over-the-counter pain medication
• A fever
• Changes in vision

Complications from sinusitis

Although rare, some serious complications⁷ can arise from a sinus infection. These include:

• Abscesses
• Meningitis: Inflammation of the membranes and fluid that surround the brain and spinal cord)
• Infection in the bones (osteomyelitis) or of the skin around the eye (orbital cellulitis)

It’s always best practice to consult your healthcare provider if you have new or worsening symptoms.

Sinus infection causes

Sinus infections are most frequently caused by bacterial infections (like strep throat) or cold or influenza viruses.

Viruses and bacteria⁸ can spread through direct person-to-person transmission. This means that you can get a sinus infection as a result of coming into contact with particles in the air left behind by an infected person’s cough or sneeze (as the bacteria can travel through saliva or mucus) or from touching surfaces that infected people have come into contact with.

The likelihood of catching an infection increases in crowded places. Schools, daycare centers, public transportation, and workplaces can all potentially harbor viruses and bacteria.

As always, it’s important to wash your hands regularly with soap and hot water—especially after touching frequently used surfaces—in order to prevent spreading or catching an illness.

The current time of year can also affect your likelihood of contracting a sinus infection. Although they can occur in any season, the common cold, the flu, and strep throat are often in higher circulation in the winter and early spring.

Because viruses and bacteria flourish in large groups of people in close contact, the beginning of the school year can present a higher risk of you or your child contracting an infection.

If you suspect that you or your child has a sinus infection, it’s important that you go to your provider in order to receive the proper diagnosis and treatment.

Who can get sinusitis?

Anyone can get sinusitis—the infection can affect both adults and children. Certain pre-existing conditions and abnormalities, however, can increase the likelihood of contracting a sinus infection.

Individuals at a higher risk of developing a sinus infection includes those who:

• Recently had or currently have a cold
• Have allergic rhinitis (hay fever) or asthma
• Have cystic fibrosis
• Have structural problems within the sinuses (such as growths/polyps on nasal or sinus linings, narrowed sinus openings, or a deviated septum)
• Have diseases that prevent the cilia from working properly
• Have a weakened or compromised immune system
• Experience drastic changes in altitude
• Smoke or are exposed to secondhand smoke
• Go to daycare or spend extended periods of time in crowded places

Do I have a sinus infection?

If you suspect that you have a sinus infection, you should make an appointment with your healthcare provider in order to receive the proper diagnosis and treatment.

Sinus infections most commonly present with postnasal drip⁹ (mucus flow down the back of the throat), pressure or tenderness on the front of the face, and congestion. Because sinus infections can follow initial illnesses like a cold or flu, these symptoms may compound on your pre-existing ones, simply making you feel even sicker.

By conducting a physical exam and potentially administering further physical or imaging tests, your healthcare provider can determine whether you do, in fact, have sinusitis.

If you have symptoms of a previously diagnosed sinus infection lasting longer than a few weeks, you may have chronic sinusitis, a prolonged condition. Chronic sinusitis may also begin as multiple bouts of acute sinusitis that do not get better or worsen over time.