The clearest sign you have a sinus infection rather than a lingering cold is symptoms that haven’t improved at all after 10 days, or symptoms that got better and then suddenly worsened. Those two patterns, along with specific types of facial pain and nasal discharge, are what separate a bacterial sinus infection from the viral illness that usually comes first.
The Key Symptoms
A sinus infection starts with cloudy or colored nasal discharge (not clear) plus at least one of two things: a stuffy, blocked nose, or pain and pressure in your face, head, or around your eyes. That combination is the baseline. Most colds produce some version of congestion and runny nose too, so what really matters is how these symptoms behave over time and whether certain red flags show up.
The symptoms that point more strongly toward a bacterial sinus infection include:
- Discolored nasal discharge, especially if it’s thicker and worse on one side
- Facial pain or pressure, particularly if it’s concentrated on one side of your face
- Fever over 100.4°F (38°C)
- A second wave of sickness after you started feeling better (more on this below)
You don’t need all of these. Having three or more makes a bacterial infection much more likely.
Where the Pain Shows Up
The location of your pain tells you which sinuses are involved. Pain in your forehead points to the frontal sinuses. Aching in your cheek, upper jaw, or upper teeth suggests the maxillary sinuses, the largest pair, which sit just above the roots of your back teeth. Pain behind your eyes typically involves the ethmoid or sphenoid sinuses, and pressure at the top of your head can signal sphenoid involvement.
Upper tooth pain catches many people off guard. The roots of your upper back teeth sit very close to your maxillary sinus cavities, and some roots actually extend into them. When those sinuses swell, the inflammation presses on nearby tooth roots and mimics a toothache. If your upper back teeth ache on one side and you also have congestion, your sinuses are the more likely culprit than a dental problem.
The 10-Day Rule and “Double Sickening”
Timing is the single most useful tool for telling a cold from a sinus infection. A typical cold improves on its own within 7 to 10 days. If your symptoms haven’t budged after 10 days, the infection has likely turned bacterial.
The other pattern to watch for is called “double sickening.” You get a cold, start to feel better after a few days, and then get noticeably worse again within 10 days of that initial improvement. New fever, worsening congestion, or a return of facial pressure after a period of relief are all classic signs. This rebound happens because a viral cold creates swelling that traps mucus in the sinuses, and bacteria take advantage of that stagnant environment to multiply.
If you’re still in the first week of symptoms and gradually improving, you almost certainly have a viral infection that will resolve without treatment.
What Mucus Color Actually Means
Green or yellow mucus is widely believed to signal a bacterial infection, but this is a myth, one that persists even among some healthcare providers. During a normal cold, mucus often starts watery and clear, then turns progressively thicker and yellow or green as your immune system ramps up. That color change comes from an increase in white blood cells and the enzymes they produce, not from bacteria specifically.
Both viral and bacterial infections can produce the same discolored mucus. So green snot alone doesn’t mean you need antibiotics. What matters more is the combination of colored discharge with other signs: one-sided facial pain, fever, and the timing patterns described above. Colored discharge is one piece of the puzzle, not the whole picture.
How It Differs in Children
Children get sinus infections too, but the symptoms can look different. Young kids only have two pairs of sinuses (the maxillary and ethmoid). The frontal sinuses behind the forehead and the sphenoid sinuses deeper in the skull don’t fully develop until the teenage years. That means younger children are less likely to report the forehead pressure adults commonly describe.
The 10-day rule still applies. Cold symptoms in a child that persist beyond 10 days without improvement raise the likelihood of a bacterial sinus infection. Children are also less likely to clearly describe facial pressure, so prolonged congestion and persistent thick nasal discharge are often the most visible clues.
How a Sinus Infection Is Diagnosed
Doctors diagnose sinus infections based on your symptoms and a physical exam. There’s no routine lab test for it. The exam typically involves pressing on your face and nose to check for tenderness and looking inside your nasal passages. For straightforward cases, that’s usually enough.
If symptoms keep coming back or don’t respond to treatment, a provider may use a nasal endoscope, a thin flexible tube with a light, to look directly into the sinus openings. CT or MRI scans are reserved for chronic or complicated cases where the doctor needs to see the sinus structures in detail or rule out other problems. Imaging isn’t standard for a first-time, uncomplicated sinus infection.
Symptoms That Need Immediate Attention
Most sinus infections are uncomfortable but not dangerous. A small number, however, can spread to nearby structures like the eyes or brain. Get medical attention right away if you notice swelling or redness around your eyes, double vision or other vision changes, a high fever, a stiff neck, or confusion. These symptoms suggest the infection may be extending beyond the sinuses and requires prompt treatment.