A sinus infection shares most of its early symptoms with a regular cold, so the biggest clue isn’t any single symptom but how long those symptoms last and how they change over time. If nasal congestion, facial pressure, and thick discharge persist for 10 days or more without improving, you’re likely dealing with a sinus infection rather than a viral cold. Here’s how to read the signals your body is giving you.
The 10-Day Rule
Most colds follow a predictable arc: symptoms peak around days three to five, then gradually improve. A sinus infection breaks that pattern. The Infectious Diseases Society of America considers a bacterial sinus infection likely when symptoms last 10 days without any improvement. That doesn’t mean 10 days of severe misery. Even low-grade congestion, drainage, and a cough that simply won’t budge past that 10-day mark qualifies.
There’s a second pattern worth knowing about, sometimes called “double sickening.” You start feeling better after a cold, then between days five and ten, symptoms come roaring back: new or worsening congestion, thicker discharge, a return of fever, or a cough that had been fading. That rebound is a strong signal that bacteria have moved into your already-inflamed sinuses.
A third scenario is a severe onset: a fever of 102°F or higher alongside thick, discolored nasal discharge and significant facial pain lasting at least three consecutive days. This presentation skips the waiting game entirely and points to a bacterial infection from the start.
Key Symptoms to Watch For
Several symptoms cluster together in a sinus infection, and some carry more diagnostic weight than others:
- Facial pressure or pain on one side. Unilateral pain, especially over the cheeks or forehead, is more suggestive of a bacterial infection than pressure felt equally on both sides.
- Tooth pain. Your upper back teeth sit just below your maxillary sinuses. When those sinuses swell and fill with fluid, the pressure can radiate downward, creating an ache that feels like a dental problem. This roughly doubles the likelihood of a bacterial cause.
- A foul smell only you notice. Detecting a persistent bad or rotten odor (called cacosmia) is actually one of the strongest individual predictors of bacterial sinusitis. It increases the probability of a bacterial infection more than almost any other single symptom.
- Thick nasal discharge with obstruction. Feeling stuffed up while also producing thick drainage, especially from one nostril, fits the pattern.
- Fever. A low-grade fever is common with colds, but a fever above 102°F combined with other sinus symptoms tilts the picture toward infection.
You can also do a simple physical check at home. Using the pads of your index and middle fingers, press firmly over your cheekbones just below each eye and over the center of your forehead. Distinct tenderness or a sharp increase in pressure pain on one side suggests inflammation in that sinus cavity. This isn’t a definitive test, but it adds useful information alongside your other symptoms.
Why Mucus Color Doesn’t Tell You Much
Green or yellow mucus is one of the most common reasons people assume they need antibiotics, but the color alone is not a reliable way to distinguish a bacterial infection from a viral one. The green tint comes from a protein inside white blood cells that your immune system deploys against any irritant, whether it’s a virus, bacteria, pollen, or even air pollution. A straightforward cold routinely produces green or yellow mucus around days three to five, right when the immune response is strongest. That doesn’t mean bacteria are involved.
What matters more than color is the combination of discharge with other symptoms (fever, facial pain, duration beyond 10 days) and whether the discharge is coming predominantly from one side.
Sinus Infection vs. Allergies
Allergies and sinus infections can both cause congestion and drainage, but they feel different in telling ways. Allergies bring itching: itchy nose, itchy eyes, sometimes itchy ears and throat. Sneezing tends to come in rapid bursts. Watery, clear discharge is the norm, and symptoms often follow a pattern tied to seasons or specific exposures like dust or pet dander. Red, watery eyes (allergic conjunctivitis) frequently accompany nasal symptoms.
A sinus infection rarely itches. The discharge tends to be thicker. Facial pain and pressure are far more prominent, and fever can occur, which allergies don’t cause. If your symptoms started after a cold and you have no history of seasonal allergies, an infection is the more likely explanation.
How It Looks Different in Children
Children get sinus infections too, but they present a bit differently than in adults. Kids often can’t articulate facial pressure, so the symptoms to watch for are a nasal discharge of any quality (it doesn’t have to be green) or a daytime cough that persists beyond 10 days without improving. The cough may worsen at night.
The same “double sickening” pattern applies: a child who seemed to be recovering from a cold but then develops worsening congestion, a new cough, or a new fever around day six or seven likely has a bacterial sinus infection. Bad breath, fatigue, and decreased appetite are common in kids with sinusitis, though they’re not specific enough on their own to confirm the diagnosis. A severe onset with a fever at or above 102.2°F plus thick, discolored discharge for three or more days warrants a call to your pediatrician.
Symptoms That Need Urgent Attention
Sinus infections rarely become dangerous, but bacteria can occasionally spread beyond the sinuses. The most concerning complication is spread to the tissues around the eye, which can cause visible swelling, redness, or a bulging appearance. Any change in vision, eye pain, or swelling around one eye alongside sinus symptoms should be evaluated quickly.
Even less commonly, infection can reach the membranes surrounding the brain, producing a severe headache and confusion. These complications are rare but serious. If you or your child develops a sudden severe headache, high fever with mental confusion, or any visual changes during a sinus infection, get medical attention the same day.