A sinus infection produces facial pain or pressure, thick nasal discharge, and congestion that either lasts longer than 10 days without improving, gets severe within the first three days, or starts to get better and then suddenly worsens. Those three patterns are the primary ways doctors distinguish a bacterial sinus infection from a regular cold, and you can use the same logic at home to figure out what you’re dealing with.
The Three Patterns That Point to a Bacterial Infection
Most sinus infections start as a viral cold. The virus inflames and swells the sinus lining, trapping mucus, and bacteria can then multiply in that stagnant fluid. Doctors rely on three specific clinical patterns to identify when that bacterial takeover has likely happened:
- Persistent symptoms: Congestion, nasal discharge, or cough lasting 10 days or more with no improvement. A typical cold should be trending better by then.
- Severe onset: A high fever (102°F or above) along with thick, discolored nasal discharge or significant facial pain that hits hard in the first three days of illness.
- Double sickening: You start to feel better after five or six days, then suddenly get worse again with a new fever, increased discharge, or returning headache. This rebound strongly suggests bacteria have moved in after the initial virus.
If none of these three patterns apply, you most likely have a viral infection that will clear on its own.
What the Mucus Color Actually Tells You
Yellow or green mucus is widely believed to signal a bacterial infection, but that’s a myth, even among some clinicians. Both viral and bacterial infections change mucus color. During a typical cold, discharge often starts clear and watery, then gradually thickens and turns yellow or green over several days as your immune system responds.
One useful distinction: with a bacterial infection, thick, discolored mucus tends to show up right at the beginning of the illness rather than building up over days. So the timing of color change matters more than the color itself. If you had clear mucus for a week that slowly turned green, that’s a normal cold progression. If your very first symptom was dense, opaque discharge alongside facial pain, that leans more bacterial.
Where the Pain Shows Up
Sinus infections cause pain in predictable locations because different sinus cavities sit behind different parts of your face. Pressure or aching across your forehead points to the frontal sinuses. Pain between or behind your eyes suggests the ethmoid sinuses. A deep ache in your cheeks or upper jaw involves the maxillary sinuses, the largest pair, which sit just above the roots of your upper back teeth.
That proximity to your teeth explains why sinus infections frequently cause what feels like a toothache. The roots of your upper molars can actually extend into the maxillary sinus cavity. When those sinuses become inflamed, the pressure irritates nearby tooth roots and mimics dental pain. If you have a toothache along with congestion and facial pressure, a sinus infection is a likely culprit, though it’s still worth having a dentist rule out cavities or gum disease first.
You can check for sinus tenderness yourself. Using your thumb, gently press in a circular motion just below your eyebrows along the bony ridge (avoiding the eye socket) to feel the frontal sinuses. Then press just below your cheekbones, slightly to each side of your nose, to check the maxillary sinuses. Mild pressure is normal. Noticeable pain or tenderness on one or both sides suggests active inflammation.
Sinus Infection vs. Allergies
Allergies and sinus infections share several symptoms: congestion, sinus pressure, and nasal discharge. The key differentiator is itchiness. Allergies typically cause itchy, watery eyes along with frequent sneezing and thin, clear discharge. Itchiness is rarely a symptom of a sinus infection.
Allergies also follow a pattern tied to triggers. Symptoms appear when you’re exposed to pollen, dust, or pet dander and improve when you remove yourself from the trigger. A sinus infection gets progressively worse regardless of your environment, and it’s more likely to involve fever, facial pain, and thick discolored mucus. If you have itchy eyes and sneeze constantly but no fever or facial pain, allergies are the more likely explanation.
How Symptoms Differ in Children
Children get sinus infections more often than adults, and their symptoms can look different. The hallmark in kids is a persistent cough and runny nose lasting more than 10 days without improvement. The nasal discharge can be any consistency or color: thin, thick, clear, or discolored. Unlike adults, who typically complain of localized facial pain, young children are more likely to be irritable and generally unwell without being able to pinpoint where it hurts.
Fever is more common in pediatric sinus infections than in adults. When children are treated appropriately, their nasal discharge and cough typically improve noticeably within 48 to 72 hours, which itself serves as a confirmation that the diagnosis was correct.
Acute vs. Chronic Sinusitis
A single episode tied to a cold is called acute sinusitis and typically resolves within a few weeks. If your symptoms persist for 12 weeks or longer, even with treatment, the diagnosis shifts to chronic sinusitis. Chronic sinusitis involves the same core symptoms (congestion, facial pressure, reduced sense of smell, thick drainage) but at a lower, grinding intensity that doesn’t fully clear up.
Chronic sinusitis has different underlying causes than the acute version. Nasal polyps, a deviated septum, or ongoing allergic inflammation can keep the sinuses perpetually swollen and poorly drained. If you’ve had repeated sinus infections or symptoms that never fully resolve between episodes, that pattern itself is an important clue that something structural or inflammatory is maintaining the problem.
What Happens at the Doctor’s Office
Most acute sinus infections are diagnosed based on your symptoms and a physical exam alone. No imaging is needed for a straightforward case. If your symptoms are persistent or recurrent, a doctor may use a nasal endoscope, a thin flexible tube with a light, to look directly at your sinus openings and check for swelling, polyps, or pus draining from the sinuses. This is usually the first step before any imaging is ordered.
CT scans are reserved for situations where treatment has failed, surgery is being considered, or the doctor suspects a complication like a spreading infection. They provide a detailed view of all the sinus cavities and surrounding bone but aren’t necessary for a typical infection.
Warning Signs That Need Immediate Attention
Sinus infections rarely cause serious complications, but when they do, the infection has typically spread to the eye socket or the brain. These complications are more common in children. Seek emergency care if you notice swelling or redness around an eye, a bulging eye, double vision or any change in vision, a severe headache that feels different from sinus pressure, a stiff neck, or a high fever that doesn’t respond to medication. These signs suggest the infection has moved beyond the sinuses and requires urgent treatment.