A sinus infection, also called sinusitis, is inflammation and swelling of the tissue lining your sinuses, the air-filled cavities inside the bones of your face. When these cavities get blocked and fill with fluid, germs grow and cause infection. Most sinus infections start as a common cold and resolve on their own within a week or two, but some persist longer and require treatment.
Where Your Sinuses Are and What They Do
You have four pairs of sinuses, each named after the facial bone it sits behind: the frontal sinuses (behind your forehead), the maxillary sinuses (behind your cheekbones), the ethmoid sinuses (between your eyes), and the sphenoid sinuses (deeper in your skull, behind the nose). Together, these eight hollow pockets serve several purposes. They produce mucus that drains into your nasal passages, trapping and flushing out germs before they can make you sick. They warm and humidify the air you breathe before it reaches your lungs. They also reduce the overall weight of your skull and act as built-in “crumple zones” that absorb some of the force during a blow to the head, protecting your brain.
When everything works normally, mucus flows freely out of your sinuses through small drainage openings. A sinus infection develops when something blocks that flow, whether it’s swelling from a cold, allergies, or a physical obstruction like nasal polyps. Trapped mucus becomes a breeding ground for viruses, bacteria, or, less commonly, fungi.
Common Symptoms
Sinus infection symptoms overlap heavily with a regular cold, which is part of what makes them frustrating to pin down. The hallmark signs include:
- Facial pain or pressure, often centered around the cheeks, forehead, or between the eyes
- Stuffy or runny nose
- Headache
- Post-nasal drip, the feeling of mucus sliding down the back of your throat
- Sore throat (often caused by that post-nasal drip)
- Cough
- Bad breath
The facial pressure tends to worsen when you bend forward. You might also notice that your sense of smell or taste is dulled, and fatigue is common because your body is fighting infection while you’re likely sleeping poorly due to congestion.
Viral vs. Bacterial Infections
The vast majority of sinus infections are caused by viruses, the same ones responsible for the common cold. A smaller percentage are bacterial. The tricky part is that yellow or green mucus, fever, and headache can show up with either type, so the color of your mucus alone is not a reliable indicator.
The clearest difference is timing. A viral sinus infection typically starts improving after five to seven days. A bacterial sinus infection tends to persist for seven to ten days or longer, and may actually get worse after the first week. Some people experience what’s sometimes called “double sickening”: they start to feel better, then symptoms ramp back up. That pattern suggests bacteria may have moved in after the initial viral infection weakened the sinus lining.
This distinction matters because antibiotics only work against bacteria. Taking them for a viral infection won’t help and can contribute to antibiotic resistance.
Acute, Chronic, and Recurrent Types
Sinus infections are classified primarily by how long they last. Acute sinusitis lasts fewer than four weeks and is by far the most common type. Most people who “have a sinus infection” are dealing with this version. Chronic sinusitis lasts longer than 12 weeks, even with treatment attempts, and involves persistent low-grade inflammation rather than a single burst of infection. Recurrent acute sinusitis means you get four or more separate infections per year, with each episode lasting seven to ten days.
Chronic sinusitis often has a different feel than acute. The dramatic facial pain and thick discharge may be less intense, replaced by a constant sense of congestion, reduced smell, and general fatigue that lingers for months. Nasal polyps, soft growths on the sinus lining, are a common contributor. When polyps grow large enough, they physically block the drainage pathways and set the stage for repeated infections.
What Triggers a Sinus Infection
Anything that causes swelling in the nasal passages or blocks sinus drainage can set the process in motion. The most common trigger is a viral upper respiratory infection, a cold. Allergies are another major contributor, since allergic inflammation narrows the drainage openings. Structural issues like a deviated septum or nasal polyps create permanent bottlenecks. Smoking and exposure to secondhand smoke irritate the sinus lining and impair the tiny hair-like structures (cilia) that sweep mucus out. Even dry indoor air during winter months can thicken mucus enough to slow drainage.
People with weakened immune systems, asthma, or conditions that affect mucus consistency tend to get sinus infections more frequently.
How It’s Treated
Since most sinus infections are viral, the first line of treatment is managing symptoms while your body clears the infection. Over-the-counter pain relievers can help with facial pressure and headache. Decongestant sprays can open up blocked passages, though using them for more than three consecutive days can backfire and cause rebound congestion. A warm compress across your face can ease the pressure, and staying well hydrated helps keep mucus thinner and easier to drain.
Saline nasal rinses are one of the most effective home treatments. Using a squeeze bottle or neti pot, you flush saltwater through your nasal passages to physically wash out mucus and irritants. The FDA emphasizes that you should only use distilled, sterile, or previously boiled water (boiled for three to five minutes and cooled). Tap water straight from the faucet can contain organisms that are safe to swallow but potentially dangerous when introduced directly into your sinuses.
If symptoms persist beyond ten days without improving, or get significantly worse after initially improving, your provider may prescribe antibiotics. The standard first choice is amoxicillin, typically for five to ten days. For people with a penicillin allergy, alternatives are available. The key point is that antibiotics are reserved for cases where bacterial infection is likely, not prescribed for every sinus infection.
When Symptoms Signal Something Serious
Sinus infections rarely lead to dangerous complications, but the sinuses sit close to the eyes and brain, so infection can occasionally spread. Seek immediate medical attention if you develop swelling or redness around the eyes, changes in vision, a severe headache unlike anything you’ve experienced before, a stiff neck, high fever with confusion, or seizures. These symptoms can indicate that infection has moved into the eye socket or toward the brain, and they require urgent evaluation.
For most people, a sinus infection is a miserable but self-limiting experience. Understanding the timeline, knowing when to wait it out, and keeping saline rinses in your medicine cabinet will get you through most episodes without needing anything more.