A sinus infection feels like a cold that won’t quit, with added pressure and pain concentrated in your face. The key signs are thick, discolored nasal discharge combined with facial pain or pressure, congestion, and a reduced sense of smell. If you have at least two of those symptoms, you’re likely dealing with sinusitis rather than a simple cold. But the details matter, because several other conditions mimic a sinus infection closely.
The Core Symptoms
Sinus infections produce a specific cluster of symptoms that, taken together, paint a clearer picture than any single sign on its own. The major ones are thick or discolored mucus draining from the front of your nose or down your throat, nasal congestion or blockage, a feeling of fullness or pressure in your face, facial pain, a weakened or lost sense of smell, and fever.
Beyond those, you may notice symptoms that seem unrelated to your sinuses: headache, ear pressure or fullness, bad breath, upper tooth pain, a cough that worsens at night, and fatigue. These are considered secondary signs, but they add weight to the diagnosis when they show up alongside the major ones. Bad breath, in particular, catches people off guard. It comes from bacteria-laden mucus draining down the back of your throat.
Where the Pain Points You
You have four pairs of sinus cavities in your skull, and where you feel pain tells you which ones are inflamed. Pressure across your forehead points to the frontal sinuses. Pain in your cheekbones or upper teeth signals the maxillary sinuses, which sit just behind your cheeks. A deep ache at the bridge of your nose involves the ethmoid sinuses. And pain behind your eyes or in your ears suggests the sphenoid sinuses, which are the deepest and farthest back.
You can check for tenderness at home with a simple technique. Using your thumb, gently press in a circular motion just below your eyebrows along the bony ridge (avoiding the eye socket itself) to test the frontal sinuses. Then press just below the cheekbones, slightly to either side of your nose, to check the maxillary sinuses. A little pressure is normal, but if either spot is noticeably tender or painful, that’s a sign of inflammation.
Why Your Upper Teeth Hurt
One of the most confusing symptoms of a sinus infection is aching in your upper back teeth. This happens because the roots of your upper molars sit extremely close to your maxillary sinuses. In some people, the tooth roots actually extend into the sinus cavity itself. When those sinuses swell, the inflammation presses directly on the nerves around those teeth.
A useful way to distinguish sinus-related tooth pain from an actual dental problem: sinus pain typically affects multiple upper teeth at once and gets worse when you bend forward or change head position. A true toothache is usually isolated to one tooth and doesn’t shift with posture. That said, infections can travel in both directions, so persistent tooth pain alongside sinus symptoms is worth getting checked.
Sinus Infection vs. a Cold
Every sinus infection starts as something else, usually a common cold. The cold virus inflames your sinus linings, and in some cases bacteria move in and set up a secondary infection. The timeline is the most reliable way to tell them apart. A typical cold improves within 7 to 10 days. If your symptoms persist beyond 10 days without getting better, a bacterial sinus infection is likely.
There’s also a pattern called “double worsening.” You start feeling better after the first week, then suddenly get worse again, with returning fever, increased facial pain, and thicker discharge. That rebound is a strong signal that bacteria have taken hold.
Sinus Infection vs. Allergies
Allergies and sinus infections share stuffy noses and congestion, which makes them easy to confuse. The distinguishing symptoms are itching and timing. Allergies cause itchy, watery eyes and frequent sneezing. Sinus infections cause facial pain, thick colored mucus, bad breath, and sometimes fever. Allergies don’t cause fever.
Timing also helps. Allergy symptoms start shortly after you’re exposed to a trigger (pollen, dust, pet dander) and last as long as the exposure continues. They can come and go with the seasons or with changes in your environment. A sinus infection builds over days, gets progressively worse, and doesn’t respond to antihistamines. Allergies can lead to sinus infections, though, because the chronic swelling they cause can block your sinuses and trap bacteria.
Sinus Infection vs. Migraine
This is a commonly missed distinction. Many people diagnosed with “sinus headaches” actually have migraines, because migraines can cause nasal congestion, a runny nose, and watery eyes. The nerves activated during a migraine are the same nerves that supply the sinuses, eyes, ears, and jaw, which is why migraines so convincingly mimic sinus problems.
The differences: migraine pain is typically throbbing or pulsating and worsens with physical movement. It often comes with nausea, vomiting, or sensitivity to light, noise, and smells. A true sinus headache produces steady pressure (not throbbing) concentrated around the eyes and cheekbones, along with thick nasal discharge and a reduced sense of smell. If you get recurrent “sinus headaches” but never have discolored mucus or fever, migraines are worth considering.
The Mucus Color Myth
Yellow or green mucus is one of the most widely believed signs of a bacterial infection, but the science doesn’t support using it as a reliable indicator. A study published in the Scandinavian Journal of Primary Health Care found that the color of nasal discharge cannot reliably distinguish between viral and bacterial infections in otherwise healthy adults. Green or yellow mucus had a sensitivity of 79% for bacterial infection but a specificity of only 46%, meaning it flags many viral infections as bacterial.
The color comes from white blood cells your immune system sends to fight any infection, viral or bacterial. So yellow or green mucus is a normal feature of your body’s immune response, not proof that you need antibiotics. The duration and pattern of your symptoms are far more useful than the color of what’s coming out of your nose.
Acute vs. Chronic Sinus Infections
An acute sinus infection lasts less than 4 weeks and is the type most people experience after a cold. Chronic sinusitis lasts longer than 12 weeks, even with treatment. The space between 4 and 12 weeks is sometimes called subacute sinusitis.
Chronic sinusitis feels different from an acute infection. The symptoms are often less intense but more persistent: ongoing congestion, reduced smell, facial pressure, and post-nasal drip that never fully clears. Fever is uncommon with chronic sinusitis. People with nasal polyps, a deviated septum, or untreated allergies are more prone to the chronic form because their sinus drainage pathways stay partially blocked.
Signs That Need Prompt Attention
Most sinus infections resolve on their own or with basic care, but certain patterns signal something more serious. Severe headache or facial pain that doesn’t respond to over-the-counter pain relief, symptoms that improve and then sharply worsen, symptoms lasting more than 10 days with no improvement, or a fever persisting beyond 3 to 4 days all warrant a visit to a healthcare provider. Having multiple sinus infections within the same year is also a reason to seek evaluation, as it may point to an underlying structural or immune issue keeping the cycle going.