Sinus headaches are caused by inflammation and pressure buildup inside the hollow cavities behind your forehead, cheeks, and the bridge of your nose. When the tissue lining these cavities swells, it traps air and mucus that can’t drain properly, creating a painful pressure differential between the inside of your sinuses and the outside atmosphere. But the picture is more complicated than most people realize: roughly 55% of people who believe they have sinus headaches actually have migraines, which mimic sinus pain closely enough to fool both patients and doctors.
How Sinus Pressure Becomes Pain
Your sinuses are air-filled pockets connected to your nasal passages through narrow drainage pathways. Under normal conditions, air flows freely in and out, keeping the pressure inside your sinuses equal to the air pressure around you. When inflammation narrows or blocks these drainage openings, the trapped air gets absorbed by the sinus lining. This creates a partial vacuum inside the cavity, pulling on the surrounding tissue and triggering pain receptors.
The pain signals travel along branches of the trigeminal nerve, the same major nerve responsible for sensation across your face. When pressure builds or tissue swells against the sinus walls, it triggers the release of chemical signals that activate pain fibers running through the forehead, upper jaw, and around the eyes. That’s why sinus headaches produce a deep, aching pressure in very specific parts of your face rather than a generalized headache across your whole head.
Where you feel the pain depends on which sinus is affected. Pressure behind your forehead points to the frontal sinuses. Pain across your cheekbones or upper teeth suggests the maxillary sinuses. A deep ache between or behind your eyes typically involves the ethmoid sinuses, which sit near the bridge of your nose.
Infections: The Most Common Trigger
Most true sinus headaches start with an infection. Your sinuses respond to an invader by producing more mucus, which creates an environment where bacteria and viruses can multiply. As the infection takes hold, the sinus tissue swells further, trapping mucus so it can’t flow out. The result is swollen, fluid-filled cavities that make your face feel achy and tender.
The vast majority of sinus infections begin as viral infections, essentially a cold that spreads into the sinuses. These typically improve on their own within 7 to 10 days. When symptoms persist beyond that window, or when they seem to improve and then suddenly worsen, a bacterial infection may have developed on top of the original viral one. Key signs that point toward a true sinus infection rather than a simple cold include thick green or yellow nasal discharge, disturbed sleep, and more severe overall symptoms. One study found that when both green nasal discharge and sleep disruption were present, there was roughly a 75% chance the problem was sinusitis rather than a straightforward upper respiratory infection.
Allergies and Sinus Pressure
Allergic reactions are another major cause of sinus headaches, and they follow a predictable two-phase pattern. In the first phase, allergens like pollen, dust mites, or pet dander land on the moist membranes inside your nose and sinuses. Your immune system responds by releasing histamine and a cascade of other inflammatory chemicals from specialized cells. This triggers the familiar symptoms: sneezing, a runny nose, watery eyes, and swelling inside the nasal passages. The excessive mucus production that follows creates sinus pressure and pain.
The second phase kicks in 4 to 8 hours after allergen exposure. This is when many people develop the headache itself, along with fatigue, irritability, and a general feeling of being unwell. The swelling that started in the nasal passages has now spread to block the sinus drainage pathways, creating the same trapped-air-and-mucus situation that infections cause. For people with chronic allergies, this cycle can repeat daily, leading to persistent or frequently recurring sinus pressure.
Structural Problems That Block Drainage
Some people are prone to sinus headaches not because of infection or allergies, but because the physical architecture of their nasal passages makes drainage difficult. A deviated septum, where the wall between your nostrils is significantly off-center, can narrow the drainage pathway on one side enough to cause recurring blockages. Nasal polyps, which are soft, painless growths on the sinus lining, can produce similar problems. Small polyps often cause no symptoms at all, but as they grow, they can block nasal passages and sinuses, leading to headaches, sinus pressure, and repeated infections.
These structural issues don’t always cause problems on their own. Often they sit quietly until a cold or allergy flare-up adds just enough extra swelling to push things past a tipping point. That’s why some people only get sinus headaches during allergy season or after a cold, even though the underlying structural issue is always there.
Weather Changes and Sinus Pain
Many people report that their sinus headaches flare up when the weather changes, and there’s a logical reason why this seems plausible. If your sinus drainage is already partially compromised, a shift in atmospheric pressure could theoretically create a mismatch between the pressure inside and outside your sinuses. This effect is well documented in extreme situations: divers and airplane passengers experience genuine barosinusitis when exposed to large, rapid pressure changes.
For routine weather changes, however, the evidence is weaker than most people assume. A 2024 analysis found that the claim that normal barometric pressure fluctuations cause sinus inflammation due to pressure differentials is unsubstantiated. The pressure shifts from a passing weather front are far smaller than those experienced during diving or flying. When weather seems to trigger a sinus headache, it may actually be triggering a migraine, which is well known to be sensitive to weather changes.
When It’s Actually a Migraine
This is the most important thing many sinus headache sufferers don’t know: more than half of self-diagnosed sinus headaches are migraines. A meta-analysis pooling data from eight studies found that 55% of patients who presented with what they believed were sinus headaches actually met the diagnostic criteria for migraine. When probable migraines and tension-type headaches were included, the number climbed to 65%.
The confusion happens because migraines can produce symptoms that feel identical to sinus problems. Migraines frequently cause pain and pressure around the forehead, cheeks, and eyes. They can trigger nasal congestion, a runny nose, and even watery eyes, all through the trigeminal nerve’s connections to the nasal passages rather than through any actual sinus disease. If you’re treating recurring “sinus headaches” with decongestants and they keep coming back, or if your headaches come with nausea, sensitivity to light, or tend to throb on one side, a migraine is the more likely explanation.
The distinction matters because sinus treatments won’t help a migraine, and effective migraine treatments exist that many sinus headache sufferers never try. If over-the-counter sinus remedies aren’t solving the problem after a few episodes, the headache itself may need a different approach entirely.
Chronic Sinusitis and Ongoing Pain
When sinus inflammation lasts 12 weeks or longer, it’s classified as chronic sinusitis. This can develop from repeated acute infections, persistent allergies, nasal polyps, or a combination of these factors. The headache pattern shifts from the intense, acute pressure of an infection to a lower-grade, persistent heaviness that worsens during flare-ups.
Certain underlying conditions make chronic sinusitis more likely and harder to treat. Asthma, immune system disorders, and a condition called ciliary dyskinesia, where the tiny hair-like structures that sweep mucus through your sinuses don’t work properly, all increase the risk. Updated clinical guidelines from the American Academy of Otolaryngology emphasize that identifying these underlying conditions is essential to managing chronic sinus problems effectively, because standard treatments alone often fall short when one of these conditions is driving the inflammation.
While rare, untreated bacterial sinus infections can occasionally spread beyond the sinuses. The most common direction of spread is into the tissues around the eye socket, causing swelling and redness around the eye. Intracranial complications are the least common but most serious. Sudden changes in vision, severe headache with high fever, or swelling around the eyes during a sinus infection warrant immediate medical attention.