A sinus infection produces three hallmark symptoms together: thick discolored nasal discharge, nasal congestion or obstruction, and facial pain or pressure. Having just one of these, like facial pain alone, isn’t enough to point to a sinus infection. The combination matters, and so does timing. Most sinus infections start as a common cold, and the key to recognizing one is knowing when a cold has crossed the line into something more.
The Three Core Symptoms
The diagnosis of a sinus infection rests primarily on what you’re experiencing, not on lab tests or imaging. The symptoms that matter most are purulent (thick, discolored) nasal drainage, a blocked or stuffy nose, and pain or pressure in your face. These three form the diagnostic foundation. Fever or facial pressure by themselves, without any nasal symptoms, don’t point to a sinus infection.
You may also notice a reduced sense of smell, a cough that worsens at night, postnasal drip (that sensation of mucus sliding down the back of your throat), headache, or fatigue. These are common supporting symptoms, but the nasal signs are what distinguish a sinus infection from other causes of facial pain or headache.
Where It Hurts Tells You Which Sinuses Are Involved
Your sinuses are air-filled pockets behind your forehead, cheeks, and eyes, and the location of your pain can reveal which ones are inflamed. Pain in your cheek or upper teeth, especially on one side, typically points to the maxillary sinuses behind your cheekbones. Tenderness above your eye near the inner edge of your eyebrow suggests the frontal sinuses. Pain at the top of your head or radiating through your temples can indicate the sphenoid sinuses, which sit deeper in the skull. That pattern is less common but tends to produce a more diffuse headache that’s harder to pinpoint.
When a Cold Becomes a Sinus Infection
Most sinus infections begin as viral colds. A typical cold peaks around days three to six and then gradually improves, with symptoms mostly or completely gone by day ten. Two patterns suggest a bacterial sinus infection has developed on top of the original virus.
The first is simple persistence: if your symptoms haven’t improved at all after ten days, bacteria have likely taken hold. The second is called “double worsening.” You start feeling better after the initial cold, then your symptoms flare up again within that ten-day window. This rebound pattern, where improvement is followed by a clear setback, strongly suggests a bacterial infection has layered onto the original viral one.
An acute sinus infection, by definition, lasts less than four weeks. If your symptoms drag on for 12 weeks or longer with documented inflammation, that crosses into chronic sinusitis, which is a different condition with its own management approach.
Green Mucus Doesn’t Mean What You Think
One of the most persistent myths, even among some clinicians, is that green or yellow mucus signals a bacterial infection that needs antibiotics. It doesn’t. Both viral and bacterial infections cause thick, discolored mucus. The color comes from white blood cells fighting the infection, not from the type of germ involved. Viruses cause the vast majority of upper respiratory infections in both children and adults, and antibiotics do nothing against them regardless of mucus color.
There is one useful timing distinction, though. With a bacterial infection, thick colored mucus often appears early. With a viral cold, the mucus tends to start clear and turn thicker and more colorful several days in. But color alone is not a reliable way to tell the difference. Duration and the overall pattern of your symptoms are far more informative.
Sinus Infection vs. Allergies
Allergies and sinus infections share nasal congestion as a symptom, which is why people often confuse them. But the two conditions feel quite different once you know what to look for.
- Itching and sneezing: Prominent with allergies, not typical of a sinus infection.
- Nasal discharge: Allergies produce thin, watery, clear drainage. Sinus infections produce thick, discolored mucus.
- Facial pain or pressure: Present with sinus infections, absent with allergies.
- Eye symptoms: About 80% of people with allergic rhinitis also have itchy, red, watery eyes. Sinus infections don’t cause eye itchiness.
- Fever: Can accompany a sinus infection, especially an acute one. Allergies don’t cause fever.
Allergies can set the stage for sinus infections by causing swelling that blocks normal sinus drainage. So it’s possible to start with allergies and develop a sinus infection on top of them, at which point you’d notice the shift toward thicker discharge and facial pressure.
Signs in Children
Children get sinus infections too, but they don’t always describe their symptoms the way adults do. In kids, the most common signs are a persistent cough (especially one that worsens at night), yellow or green nasal discharge, nasal congestion with mouth breathing or snoring, headache, and facial pain or pressure. Fever is more often present in children with acute sinus infections than in adults. A cold that lingers well beyond ten days or a cough that just won’t quit are the patterns that most often lead to a sinus infection diagnosis in children.
Symptoms That Need Urgent Attention
Sinus infections occasionally spread beyond the sinuses into surrounding structures, including the eye socket and the lining of the brain. This is rare but serious. Seek immediate medical care if you develop swelling or redness around your eyes, double vision or other visual changes, swelling of your forehead, a severe headache that doesn’t respond to typical pain relief, a stiff neck, or confusion. These symptoms suggest the infection may be affecting nearby tissues and require prompt evaluation.