Chronic rhinosinusitis is long-term inflammation of the sinuses and nasal passages that lasts at least 12 weeks, even with treatment attempts. It affects roughly 8.7% of the global population, making it one of the most common chronic conditions. Unlike a regular sinus infection that clears up in a week or two, chronic rhinosinusitis (CRS) involves persistent swelling of the sinus lining that disrupts drainage, breathing, and quality of life.
Core Symptoms
A CRS diagnosis requires at least two of the following symptoms persisting for 12 weeks or longer:
- Thick or discolored nasal drainage, either out the front of the nose or dripping down the back of the throat
- Nasal congestion that doesn’t resolve with typical cold remedies
- Facial pain, pressure, or fullness, often concentrated around the cheeks, forehead, or between the eyes
- Reduced sense of smell
Beyond these hallmark symptoms, CRS can produce a surprisingly wide range of less obvious problems: postnasal drip, a chronic cough that doesn’t seem productive, sore throat, bad breath, fatigue, ear fullness, dizziness, and unexplained changes in taste. Many people live with several of these for months before connecting them to a sinus problem.
Two Main Types
CRS is broadly divided into two forms based on whether nasal polyps are present. Nasal polyps are soft, painless growths that develop on the lining of the sinuses or nasal passages. The type with polyps (CRSwNP) accounts for a smaller share of cases, with a global prevalence of about 0.65%, and tends to be driven by a specific pattern of immune overactivity involving eosinophils, a type of white blood cell associated with allergic inflammation. The type without polyps (CRSsNP) is more common and more variable in its underlying inflammation.
This distinction matters because the two types often respond differently to treatment. CRSwNP is more likely to cause a significant loss of smell and tends to recur after surgery. CRSsNP may involve more pain and pressure but can sometimes be managed more effectively with standard medical therapy.
What Happens Inside the Sinuses
In a healthy nose, the sinus lining produces a thin layer of mucus that traps particles and drains through small openings into the nasal cavity. In CRS, the lining becomes chronically inflamed and swollen, narrowing or blocking those drainage pathways. Mucus builds up, creating an environment where bacteria can thrive and further irritate the tissue.
Over time, the inflammation triggers structural changes in the sinus lining itself. The tissue thickens, mucus-producing glands multiply, and the delicate cells that sweep mucus out of the sinuses become damaged. In polyp-forming CRS, immune cells release signals that cause fluid to accumulate in the tissue, forming the grape-like growths that can fill the nasal cavity. These changes are collectively called mucosal remodeling, and they explain why CRS is so persistent: the tissue itself has been physically altered by months or years of inflammation.
What Causes It
There is rarely a single cause. CRS typically develops from a combination of factors that keep the sinuses inflamed. Allergies are a major contributor, as ongoing allergic reactions in the nose maintain the swelling that blocks sinus drainage. Structural issues like a deviated septum or narrow sinus openings can make someone more prone to blockages. Asthma and sensitivity to aspirin are strongly linked to the polyp-forming type.
Bacterial infections play a role, but not in the straightforward way most people assume. CRS is not simply an infection that won’t go away. Rather, the inflamed environment allows bacteria to colonize the sinuses, which then worsens the inflammation in a self-reinforcing cycle. Some patients harbor unusual bacteria like Pseudomonas or Staphylococcus aureus, which can be particularly difficult to clear. Environmental factors like air pollution, cigarette smoke, and occupational dust exposure also contribute by constantly irritating the sinus lining.
How It Is Diagnosed
Diagnosis starts with your symptoms and their duration. At least two of the core symptoms must be present for 12 or more weeks, and one of them must be either nasal blockage or nasal discharge. But symptoms alone aren’t enough to confirm the diagnosis. Doctors look for objective evidence of inflammation using one or both of two tools.
Nasal endoscopy involves inserting a thin, flexible camera into your nose to directly visualize the sinus openings, look for polyps, and check for pus or swelling. A CT scan of the sinuses provides a detailed picture of the bony sinus structures and can reveal mucosal thickening, blocked drainage pathways, or polyps that aren’t visible on endoscopy. CT imaging is generally ordered after an initial course of medical treatment, not as a first step, so that the scan reflects your baseline disease rather than a temporary flare.
First-Line Treatment
The initial approach to CRS is medical, not surgical. Two treatments form the foundation. Saline nasal irrigation, done once or twice daily with a squeeze bottle or neti pot, physically flushes mucus, bacteria, and inflammatory debris from the sinuses. It sounds simple, but consistent irrigation is one of the most effective things you can do. The second cornerstone is a corticosteroid nasal spray, used as two sprays in each nostril daily for a minimum of eight weeks. These sprays reduce the swelling that blocks sinus drainage and are safe for long-term use.
For bacterial flares, doctors may prescribe a course of antibiotics lasting two to four weeks, ideally guided by a culture showing which bacteria are present. Oral steroids are sometimes used for short bursts to knock down severe inflammation, particularly when polyps are obstructing the nose. Treating underlying allergies with antihistamines or immunotherapy can also help by reducing one of the drivers of chronic inflammation.
When Surgery Becomes an Option
Surgery is considered when you’ve completed a full course of medical therapy and your symptoms haven’t improved enough. This is called “medically refractory” disease. The standard procedure, functional endoscopic sinus surgery (FESS), is performed entirely through the nostrils with no external incisions. The surgeon widens the natural drainage openings of the sinuses and removes polyps, thickened tissue, or bone that is blocking airflow. The goal is to restore ventilation and drainage so that medications like nasal sprays and irrigations can actually reach the sinus lining and work effectively.
FESS is not a cure. It creates better anatomy, but the underlying tendency toward inflammation remains. Most people still need ongoing medical management after surgery to prevent recurrence, especially those with nasal polyps.
Biologic Therapies for Severe Cases
For people with CRSwNP who keep developing polyps despite surgery and standard treatments, a newer class of medications called biologics has changed the landscape. These are injectable drugs that target specific molecules in the inflammatory chain. Three are currently approved in the United States for nasal polyps: one that blocks two key inflammatory signals involved in polyp growth (approved 2019), one that prevents an allergic antibody from activating immune cells (approved 2020), and one that targets a signal responsible for activating eosinophils (approved 2021).
Biologics can shrink polyps, restore the sense of smell, and reduce the need for repeat surgeries. They are typically reserved for patients with recurrent or severe disease because they require ongoing injections and are expensive. Your doctor would evaluate whether your specific pattern of inflammation matches the target of a given biologic before starting treatment.
Potential Complications
CRS is not life-threatening for most people, but because the sinuses sit directly below the brain and beside the eye sockets, untreated or severe disease can occasionally spread. Orbital complications range from mild swelling of the eyelid to more serious infections of the tissue around the eye, abscess formation, and in rare cases, vision loss. Intracranial complications like meningitis or blood clots in the veins near the brain are uncommon but represent the most dangerous end of the spectrum. These complications are far more likely in acute infections than in typical chronic disease, but they underscore why persistent sinus symptoms deserve proper evaluation rather than indefinite self-treatment with over-the-counter decongestants.