A bacterial sinus infection, or sinusitis, will usually resolve by itself. In rare cases, untreated sinusitis may spread and cause serious complications.

The vast majority of sinus infections are viral, although they can also be bacterial or fungal. These infections develop when fluid builds up in the sinuses, allowing germs to grow.

Bacterial sinusitis can also develop when the sinuses become inflamed from another cause, such as a viral infection.

A bacterial sinus infection may resolve without medical intervention, but people need treatment if symptoms persist.

Treating an ongoing bacterial sinus infection can help prevent the infection from spreading to other areas of the body, which can be dangerous.

This article examines what might happen with an untreated bacterial sinus infection, potential complications, treatments, and when to consult a doctor.

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A bacterial sinus infection will often resolve by itself without treatment. However, an untreated bacterial sinus infection can cause complications.

It can resolve without treatment

According to the Centers for Disease Control and Prevention (CDC), most sinus infections will get better independently without needing treatment.

Antibiotics are unnecessary in many cases, and a doctor may advise waiting and monitoring symptoms before prescribing them. Antibiotic treatment may only be necessary if symptoms do not improve within 7–10 days.

The infection can spread to the eyes

In rare cases, a bacterial sinus infection may spread to nearby areas such as the eyes. This can cause:

  • Preseptal cellulitis: This refers to inflammation of the orbital septum, which is the tissue that divides the eyelids and the orbit.
  • Orbital cellulitis: This is an infection of the muscles and fat surrounding the eye.
  • Subperiosteal abscess: This refers to a collection of pus inside the eye socket.
  • Cavernous sinus thrombosis: This involves a blood clot in the cavernous sinuses, which are hollow spaces behind each eye socket.

In most cases, antibiotics can quickly and effectively treat a sinus infection that has spread to the eyes. However, in some cases, surgery may be necessary.

The infection can spread to the bones

An infection of the frontal sinuses may cause osteomyelitis, a severe complication that can be life threatening. Osteomyelitis is an inflammation of the bones due to infection.

However, antibiotics and surgical procedures can help treat it.

Spreads to the brain

Some of the sinus cavities are close to the brain. Without treatment, sinusitis has the potential to spread to the brain. This is rare but can be life threatening, and prompt treatment is essential.

A sinus infection which spreads to the brain may cause:

  • subdural hematoma, which is the pooling of blood on the surface of the brain
  • epidural hematoma, a pooling of blood between the skull and the protective covering of the brain
  • subdural abscess, which develops on the surface of the brain
  • epidural abscess, which is an abscess between the skull and the protective covering of the brain
  • meningitis

Most people will not need treatment for a sinus infection.

A person can instead treat the symptoms at home by getting plenty of rest, remaining hydrated, taking over-the-counter (OTC) medications, and using a neti pot or other nasal irrigation devices. Many sinus infections can resolve within 7–10 days without antibiotic treatment,

However, the CDC advises speaking with a doctor if a sinus infection lasts longer than 10 days without improvement.

Before prescribing antibiotics, a doctor may recommend watchful waiting. This involves waiting 2–3 days to monitor symptoms and check if antibiotics are necessary.

A doctor may instead prescribe antibiotics but suggests people wait 2–3 days before filling the prescription to see if symptoms improve.

The CDC advises that people speak with a doctor if:

  • they have severe facial pain or headache
  • symptoms last more than 10 days without signs of improvement
  • symptoms worsen after initially improving
  • they have a fever that lasts more than 3–4 days
  • a person has had multiple sinus infections in the past year

People may be able to ease symptoms of a bacterial sinus infection at home with the following treatments:

  • applying a warm compress to the nose and forehead area to help relieve pressure
  • breathing in steam from a hot shower or bowl of hot water
  • using a saline nasal spray
  • using nasal saline rinses to help clear the nasal passages
  • taking OTC pain relief medication

In some cases, people may require medications such as:

  • nasal decongestant sprays to help clear the sinus passages
  • antihistamines to reduce swelling in the sinus passages
  • combination nasal decongestants and antihistamines
  • topical nasal corticosteroids to reduce inflammation

If symptoms of a bacterial sinus infection do not improve, people may require antibiotics. This may include treatment with amoxicillin and clavulanate.

The following are answers to common questions about bacterial sinus infections.

How serious is a bacterial sinus infection?

Although bacterial sinus infections can have serious complications, these are rare and only occur in around 1 in 1,000 cases.

These complications can include infections spreading to the eyes, brain, or bones. Without treatment, they can be life threatening.

What are the stages of a bacterial infection?

The stages of a bacterial infection are incubation, prodromal, acute period, decline, and convalescence.

The incubation state is the time from first exposure to the infection until the first signs or symptoms appear.

In the prodromal state, the immune system begins to react to the infection, and early symptoms develop.

The acute period is the time in which symptoms peak as the immune system fights the infection.

Eventually, a person will experience the decline stage, where the infection decreases, and symptoms begin to lessen.

Finally, people will reach the convalescence stage, which is when they start recovering and symptoms ease.

People can still transmit the infection to others during the convalescence stage.

How can you tell if a bacterial sinus infection has spread to the brain?

If a sinus infection has spread to the brain, it may cause severe symptoms. These symptoms include a severe headache, a stiff neck, vision changes, a persistent fever, altered mental status, confusion, and lethargy.

If people have any of these symptoms with a sinus infection, they must seek medical attention immediately.

A bacterial sinus infection can resolve without treatment. However, if symptoms persist without improvement, people will need to contact a doctor to prevent complications.

Although rare, an untreated sinus infection can lead to serious complications if it spreads to the brain or eyes.

Treatments can include over-the-counter or prescription medications, such as decongestants and nasal sprays. A doctor may prescribe antibiotics if a bacterial sinus infection is not clearing.