The telltale signs of a sinus infection are thick, discolored nasal discharge combined with nasal congestion and facial pain or pressure. If those symptoms persist for 10 days or more without improving, or if they start to get better and then suddenly worsen, you’re likely dealing with a bacterial sinus infection rather than a common cold.
The Core Symptoms
A sinus infection, or sinusitis, produces three hallmark symptoms that tend to appear together: purulent (thick, cloudy, or discolored) nasal drainage, a stuffy or blocked nose, and pain or pressure in your face. You might also notice a reduced sense of smell, a feeling of fullness in your ears, or a cough that worsens at night as mucus drains down the back of your throat.
Where the pain shows up depends on which sinuses are inflamed. Your frontal sinuses sit in the lower part of your forehead, near the inner edges of your eyebrows, so infection there creates a headache-like pressure right above your eyes. Your maxillary sinuses are behind your cheekbones, just under your eyes. When those are affected, you’ll feel aching across your cheeks or even in your upper teeth, since the roots of those teeth sit very close to the maxillary sinus cavity. Some people visit the dentist for a toothache only to discover the real problem is sinus inflammation.
Fatigue and a general feeling of being unwell are common. Fever can occur but isn’t present in every case, so don’t rely on a normal temperature to rule out a sinus infection.
How Long Symptoms Last Matters Most
Duration is the single most important clue for figuring out what you’re dealing with. Most sinus infections start as viral infections, essentially a cold that settles into the sinuses. A viral sinus infection typically begins improving after five to seven days. A bacterial sinus infection often persists for seven to ten days or longer, and it may actually worsen after the seven-day mark.
Clinical guidelines use a clear rule: if your symptoms haven’t improved at all after 10 days, a bacterial infection is the likely cause. The other red flag is a pattern called “double sickening.” This is when you start feeling better around days three to five, then take a noticeable turn for the worse between days five and ten, with returning or worsening congestion, pain, and fever. Double sickening is one of the strongest indicators that bacteria have taken hold.
If symptoms drag on for 12 weeks or more, the condition is classified as chronic sinusitis, which has different causes and treatment approaches than a short-term infection.
What Mucus Color Actually Tells You
Green or yellow mucus is widely believed to signal a bacterial infection, but this is a myth, even among some healthcare providers. Both viral and bacterial infections can change the color of your nasal mucus. The color shift comes from white blood cells and enzymes your immune system releases to fight any kind of infection, not specifically bacteria. So while thick, discolored discharge is part of the diagnostic picture, the color alone can’t tell you whether you need antibiotics.
What does matter is the overall pattern: discolored mucus plus persistent congestion plus facial pressure, lasting beyond that 10-day window or following a double-sickening trajectory.
Sinus Infection vs. Allergies
Allergies and sinus infections share some symptoms, particularly nasal congestion, drainage, and a reduced sense of smell. The distinguishing features are straightforward. Allergies cause itching: itchy nose, itchy eyes, and frequent sneezing. Sinus infections don’t. Allergies also produce thin, clear, watery discharge, while sinus infections tend toward thicker, discolored mucus.
Facial pain and pressure are much more characteristic of a sinus infection than of allergies. If you have seasonal allergy patterns, you probably already recognize the sneezing and itching that come with them. When facial pain or yellowish-green discharge enters the picture on top of your usual allergy symptoms, that’s a sign the congestion may have progressed into an actual infection. People with recurring allergies are at higher risk for sinus infections because chronic nasal inflammation makes it easier for bacteria to take hold.
The Tooth Pain Connection
Upper tooth pain without an obvious dental cause can be a surprising symptom of sinusitis. The roots of your upper back teeth extend very close to the floor of the maxillary sinuses. In some people, they actually protrude into the sinus cavity. When those sinuses swell, the pressure pushes directly against the tooth roots, creating pain that feels identical to a cavity or abscess.
The connection also works in reverse. A dental infection in an upper tooth can spread into the sinus cavity and cause persistent sinusitis. If you have a stubborn sinus infection that keeps returning on one side and doesn’t respond well to typical treatment, a dental problem may be the underlying cause. In cases of unexplained upper tooth pain, it’s worth seeing both a dentist and a doctor to determine which direction the problem is flowing.
Symptoms That Need Urgent Attention
Most sinus infections resolve on their own or with straightforward treatment, but in rare cases, the infection can spread to nearby structures. Seek immediate medical care if you develop any of the following:
- Swelling, redness, or pain around your eyes, which can signal the infection is spreading to the eye socket
- Vision changes, including double vision or blurring
- High fever that doesn’t respond to over-the-counter medication
- Severe headache with a stiff neck, which could indicate the infection has reached the membranes surrounding the brain
- Confusion or altered mental state
These complications are uncommon, but they can become serious quickly. An infection that reaches the eye socket can threaten vision, and one that reaches the brain’s protective membranes can cause meningitis.
Putting the Clues Together
No single symptom confirms a sinus infection. The diagnosis comes from combining what you feel with how long you’ve felt it. Thick nasal discharge plus facial pain plus congestion is the symptom triad. Duration beyond 10 days, or a clear double-sickening pattern, separates bacterial from viral. Itching and sneezing point toward allergies instead. And one-sided upper tooth pain with no dental explanation can be the clue that ties everything together.
If your symptoms fit the bacterial pattern, that’s when treatment with antibiotics becomes a reasonable conversation. For the first week or so, the best approach is supportive care: saline nasal rinses, staying hydrated, and using a humidifier to keep your nasal passages moist. Most viral sinus infections clear without medication, and jumping to antibiotics too early won’t speed recovery when a virus is the cause.