Sinusitis is inflammation of the tissue lining your sinuses, the air-filled cavities in your face. It affects roughly 29 million adults in the United States each year, about 12% of the adult population. Most cases start when something blocks the normal drainage of your sinuses, allowing mucus to build up and, in many cases, bacteria or viruses to take hold. The result is facial pressure, congestion, and sometimes significant pain that can last anywhere from a few days to several months.
How Your Sinuses Work
You have four paired sets of sinuses carved into the bones of your skull: the maxillary sinuses (in your cheekbones), the frontal sinuses (above your eyes), the ethmoid sinuses (between your eyes), and the sphenoid sinuses (deeper, behind your nose). All of them are lined with a thin layer of tissue that produces mucus, which normally drains through narrow passages into your nasal cavity.
The most important of these passages is a bottleneck called the ostiomeatal complex. It handles drainage from the frontal, ethmoid, and maxillary sinuses. When this area swells shut from a cold, allergies, or other irritation, mucus gets trapped. That warm, moist, stagnant environment is where infections begin.
What Causes Sinus Infections
The most common trigger is a viral upper respiratory infection, a regular cold. The virus inflames the sinus lining, which swells enough to block drainage. Most of the time the infection stays viral and resolves on its own. In a smaller number of cases, bacteria move into the trapped mucus and cause a secondary bacterial infection, which tends to produce more severe or longer-lasting symptoms.
Several factors make some people more prone to sinusitis than others:
- Allergies. Hay fever and other allergic reactions cause chronic swelling inside the nose, which narrows drainage pathways.
- Nasal polyps. These soft, painless growths in the nose or sinuses can physically block airflow and drainage. They’re more common in people with asthma, cystic fibrosis, or sensitivity to certain pain relievers.
- A deviated septum. A crooked wall between the nostrils can obstruct one side of the nose and make drainage uneven.
- Environmental irritants. Cigarette smoke, air pollution, and dry indoor air can all irritate sinus tissue and promote swelling.
Acute, Subacute, and Chronic Sinusitis
Sinusitis is classified by how long it lasts. Acute sinusitis involves symptoms that last less than four weeks and typically improve with basic treatment. Subacute sinusitis describes symptoms that linger between four and eight weeks, often because the initial episode didn’t fully resolve. Chronic sinusitis means symptoms have persisted for 12 weeks or longer, sometimes with repeated flare-ups layered on top of a low-grade baseline of congestion and pressure.
The distinction matters because acute sinusitis is usually a one-time event triggered by a cold, while chronic sinusitis often points to an underlying structural problem, ongoing allergies, or persistent inflammation that needs a different approach to treatment.
Symptoms and Where the Pain Shows Up
The hallmark symptoms of sinusitis are facial pressure, nasal congestion, thick discolored mucus, and a reduced sense of smell. Many people also experience fatigue, post-nasal drip (mucus running down the back of the throat), and a cough that worsens at night when lying down.
Where you feel pain can actually tell you which sinuses are involved. Maxillary sinusitis causes aching in the cheeks, just below the eyes, and can mimic a toothache in the upper jaw. Frontal sinusitis produces a headache concentrated across the forehead. Ethmoid sinusitis causes pain behind and between the eyes, sometimes with tearing and a headache that people describe as a splitting sensation. Sphenoid sinusitis is less localized and can cause a vague ache that radiates to the front or back of the head, making it harder to pinpoint.
How Sinusitis Is Diagnosed
In the vast majority of cases, a doctor diagnoses sinusitis based on your symptoms and a physical exam. No imaging is needed for a straightforward case. If you describe facial pressure, congestion, and thick nasal discharge lasting more than a week, that’s typically enough information to make the call.
CT scans and nasal endoscopy (a thin camera inserted into the nose) are reserved for situations where symptoms keep coming back, don’t respond to treatment, or when a doctor suspects something more complicated like an abscess or structural problem. A CT scan is also standard before sinus surgery, since it gives a detailed map of the sinus anatomy. For a first episode of uncomplicated sinusitis, imaging would be overkill.
Treatment and the Watchful Waiting Approach
Because most acute sinusitis cases are viral, antibiotics won’t help the majority of people who walk into a clinic with sinus symptoms. Current guidelines recommend a period of watchful waiting before prescribing antibiotics, even when bacterial sinusitis is suspected. The reasoning is that many bacterial sinus infections also clear on their own.
Here’s how the timeline typically works: a clinical diagnosis of bacterial sinusitis usually requires at least 10 days of symptoms. From that point, guidelines suggest an additional observation period of three to seven days, meaning symptoms may need to persist for roughly two to two and a half weeks total before antibiotics are considered. If symptoms are worsening, are unusually severe, or you have a weakened immune system, that waiting period may be shortened.
During the waiting period, treatment focuses on managing symptoms:
- Saline nasal irrigation. Rinsing your sinuses with a saltwater solution (using a neti pot, squeeze bottle, or similar device) is one of the most consistently effective self-care measures. Research from the University of Wisconsin found that people who used nasal irrigation had fewer symptoms, better quality of life, and used antibiotics and nasal sprays less often. Many people settle into a pattern of about three rinses per week, either on a set schedule or as needed when symptoms flare.
- Decongestant sprays and oral decongestants. These can temporarily open blocked passages. Spray decongestants should be limited to a few days to avoid rebound congestion.
- Pain relievers. Over-the-counter options can help with facial pain and headaches.
- Steam and humidity. Breathing warm, moist air from a shower or humidifier can thin mucus and ease pressure.
For chronic sinusitis, treatment often shifts toward controlling the underlying inflammation. Steroid nasal sprays are a mainstay for reducing swelling over weeks and months. If nasal polyps or a deviated septum are blocking drainage, surgery to physically open the sinus passages may be recommended after other options have been exhausted.
Rare but Serious Complications
Sinus infections rarely cause dangerous complications, but “rarely” isn’t “never.” Because the sinuses sit close to the eyes and brain, an infection that spreads beyond the sinus walls can lead to serious problems. Orbital complications (infection spreading to the tissue around the eye) are the most common of these uncommon events. They occur more often in children and can cause swelling, redness, and bulging of the eye.
In the most severe cases, untreated or incompletely treated sinusitis can lead to infections reaching the brain, including meningitis or blood clots in the veins that drain the brain. These complications can occur in otherwise healthy people, though they’re more likely in those with weakened immune systems from conditions like uncontrolled diabetes, kidney failure, or certain cancers. Worsening headache, high fever, visual changes, or swelling around the eye during a sinus infection are signs that warrant urgent medical attention.