Sinus Infection

How to tell if a sinus infection has spread to your brain

It is extremely rare for bacteria from a sinus infection to infect the brain. But it does happen. Here’s what to look out for.
Side view of calm Hispanic woman in casual clothes closing eyes and resting on couch near table with smartphone and notebook while taking break in home studies in light living room.

Key points:

  1. Paranasal sinus cavities are in the skull and close to the brain.
  2. Viruses cause most sinus infections. But bacteria can get stuck in the sinuses and replicate if an infection lingers too long.
  3. In extremely rare cases, this bacteria can travel to the brain and cause a life-threatening condition.

A group of researchers once used thermal cameras to track the temperature of study participants as they told a lie. Compared to controls, lying participants showed increased temperature in their hands and noses!

Why? Telling a lie triggers anxiety. When anxious, a part of our brain called the insula activates. The insula controls body temperature and helps regulate emotion. So the anxiety of telling a lie triggers the shift.

That’s not the only way the nose and brain are connected. When you have a sinus infection, you may worry that it will spread to where you don’t want it to! Read on to learn why it’s uncommon for a sinus infection to spread to the brain. Plus, how to tell when symptoms require prescription sinus infection treatment.

How do nasal passages work?

Nasal passages connect various sinuses—empty areas behind the cheeks and forehead. Sinuses make mucus, which carries out the irritants that can make us sick.

But when something irritates our sinuses—like an allergy or virus. The empty chambers fill with mucus, and we get an inflamed nose and sinuses, runny nose, stuffy nose, headache and other common symptoms.

Can a sinus infection get close to the brain?

Acute sinusitis can allow bacteria to travel to our brain when left untreated for too long. Before you panic, know this is extremely rare.

The paranasal sinus cavities are inside the skull, close to our brain. Our brain is protected by a blood-brain barrier that only lets some fluids and nutrients pass in.

Most sinus infections are caused by a virus like the common cold or influenza. Children get an average of five infections yearly, and most of us clear them on our own without any treatment. But if the virus lingers and knocks our immune system, bacteria can root down, replicate and spread, causing a bacterial infection.

Studies estimate this only happens in .5% to 2% of sinus infections. So the odds of having a wealth of bacteria eager to travel to the brain are extremely low.

But when that does happen, a subdural empyema may follow, causing a pus of white blood cells to collect between brain layers. This can lead to brain swelling, seizures, confusion and more.

When is a sinus infection life-threatening?

When bacteria travel to the brain, an abscess, meningitis or another life-threatening condition may follow.

Again, this is rare—in only 1 to 6 cases per million people. But a headache lasting over a week, neurological signs like an altered mental state, and forehead swelling may signify that something has gone dangerously wrong. If caught too late or left untreated, these severe symptoms could lead to seizures, coma and death.

Banner advertising Dr. B's services for sinus-infection treatments

When to see an ear, nose and throat doctor

Life-threatening sinusitis usually only happens when a severe infection is not diagnosed or treated promptly.

Severe infection symptoms include:

  • Severe headache
  • Facial pain
  • Symptoms that last over 10 days
  • Symptoms that get better and then worse again
  • Fever that lasts longer than 3-4 days

Even if you have a severe sinus infection, your provider may have you wait a few days longer to see if your immune system can fight the infection. They may also suggest using nasal sprays, humidifiers and over-the-counter medications to reduce symptom severity.

Antibiotics only work for bacterial infections—not viral infections. As it usually takes a few weeks for a viral infection to cause a bacterial infection, don’t be surprised if your physician doesn’t prescribe antibiotics immediately.

If you have severe or lingering sinusitis symptoms and seek treatment—or just peace of mind—come to Dr. B.

Our online sinus infection consultations cost just $15. If a licensed provider recommends prescription treatment, they’ll send it to your chosen pharmacy. We’ll even help you find the lowest cost for your medication and your local pharmacies. Get started today!


Benevides, G. N., et al. (2015). Bacterial sinusitis and its frightening complications: Subdural empyema and Lemierre syndrome. Autopsy & Case Reports.

Centers for Disease Control and Prevention. Sinus infection.

Greenlee JE. (2003). Subdural Empyema. Current Treatment Options in Neurology.

Jafari, A., et al. (2021). Association of sinonasal inflammation with functional brain connectivity. JAMA Otolaryngol Head and Neck Surgery.

Michali, M. C., et al. (2021). Parenchymal brain abscess as an intracranial complication after sinusitis. Cureus.

Moliné, A., et al. (2018). The mental nose and the Pinocchio effect: Thermography, planning, anxiety, and lies. Journal of Investigative Psychology and Offender Profiling.

Mount Sinai. Sinusitis.

Sande, M. A., et al. (2004). Acute community-acquired bacterial sinusitis: continuing challenges and current management. Clinical Infectious Diseases.

Sign up for the free Dr. B newsletter for a weekly report on the latest in healthcare + research-based advice for staying healthy and mentally well.

Related articles