What Is Sinusitis (Rhinosinusitis)? Symptoms, Types and Treatment

Created: 07.10.2024 · Last Updated: 11.08.2026 · Category: Ear, Nose and Throat · Prepared by the Academic Hospital Web and Editorial Board.

Sinusitis is inflammation of the paranasal sinuses around the nose and usually involves inflammation of the nasal lining as well. For this reason, the term rhinosinusitis is commonly used in contemporary medical practice.

Most acute rhinosinusitis develops during a viral upper respiratory infection such as the common cold and improves without antibiotics. Persistent symptoms, worsening after initial improvement or symptoms lasting for many weeks require a different assessment.

Yellow or green nasal mucus does not by itself prove that sinusitis is bacterial. Duration, progression of symptoms, nasal obstruction and facial pain or pressure should be considered together.

What Are the Sinuses?

The paranasal sinuses are air-filled spaces within the bones around the nose and eyes.

They include:

  • Maxillary sinuses: In the cheek area
  • Frontal sinuses: In the forehead
  • Ethmoid sinuses: Between the eyes
  • Sphenoid sinuses: Deeper behind the nasal cavity

The sinus lining produces mucus, which normally drains into the nasal cavity through small openings.

Healthy sinus function depends on open drainage pathways and effective mucociliary clearance.

What Is Sinusitis?

When the nasal and sinus lining becomes inflamed, swelling can narrow the drainage pathways and increase mucus production.

This can lead to:

  • Nasal obstruction
  • Nasal or postnasal discharge
  • Facial pain, pressure or fullness
  • Reduced sense of smell

Rhinosinusitis does not automatically mean a bacterial infection. Most acute cases are viral, while chronic rhinosinusitis is better understood as a persistent inflammatory disorder rather than simply a prolonged infection.

What Are the Types of Sinusitis?

Acute Rhinosinusitis

Acute rhinosinusitis typically involves cloudy or coloured nasal drainage together with nasal obstruction and/or facial pain, pressure or fullness lasting for up to 4 weeks.

Most episodes are caused by viral infections.

Acute Bacterial Rhinosinusitis

Bacterial rhinosinusitis becomes more likely when:

  • Symptoms continue for 10 days or longer without improvement
  • Symptoms worsen again after initially improving

Recurrent Acute Rhinosinusitis

This describes repeated episodes of acute rhinosinusitis with a return to a healthy or symptom-free baseline between episodes.

Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is characterised by sinonasal inflammation and associated symptoms lasting for more than 12 weeks.

CRS may occur:

  • With nasal polyps
  • Without nasal polyps

What Causes Sinusitis?

Viral upper respiratory infections are the most common triggers of acute rhinosinusitis.

Factors associated with sinonasal inflammation or an increased risk of rhinosinusitis include:

  • Viral respiratory infections
  • Some bacterial infections
  • Allergic rhinitis
  • Smoking and second-hand smoke
  • Nasal polyps
  • Certain anatomical narrowing
  • Impaired immune function
  • Asthma
  • Aspirin-exacerbated respiratory disease
  • Rare disorders affecting mucociliary function
Going outside with wet hair or being exposed to cold weather is not considered a direct cause of sinusitis. Viral respiratory infections are more common during colder seasons and may indirectly lead to more episodes of acute rhinosinusitis.

What Are the Risk Factors for Sinusitis?

Risk can be increased by:

  • Frequent upper respiratory infections
  • Allergic rhinitis
  • Nasal polyps
  • Smoking or second-hand smoke exposure
  • Asthma
  • Immunocompromised states
  • Conditions that impair mucociliary clearance

A deviated nasal septum or other anatomical variation can contribute to impaired sinus drainage in selected patients, but it is not the sole or universally most important cause of sinusitis.

What Are the Symptoms of Sinusitis?

Possible symptoms include:

  • Nasal blockage or congestion
  • Nasal discharge
  • Postnasal drip
  • Facial pain, pressure or fullness
  • Reduced or lost sense of smell
  • Headache
  • Cough
  • Bad breath
  • Fatigue
  • Fever during an acute infection

These symptoms are not specific to sinusitis. Migraine, allergic rhinitis, dental disease and other facial or nasal conditions can cause similar complaints.

How Can Viral and Bacterial Sinusitis Be Distinguished?

Acute viral rhinosinusitis is more likely when symptoms have been present for fewer than 10 days and are not worsening.

Acute bacterial rhinosinusitis becomes more likely when:

  • Symptoms persist for 10 days or longer without meaningful improvement
  • Symptoms initially improve but then worsen again within the early course of the illness

The latter pattern is often referred to as double worsening.

The colour of nasal mucus alone should not determine whether antibiotics are prescribed.

How Is Sinusitis Diagnosed?

Acute rhinosinusitis is usually diagnosed from:

  • The type of symptoms
  • Their duration
  • The pattern of improvement or worsening
  • Nasal and ENT examination

Routine X-rays or CT imaging are not recommended for uncomplicated acute rhinosinusitis.

For chronic rhinosinusitis, the clinical diagnosis should be supported by objective evidence of sinonasal inflammation.

This can be documented using:

  • Anterior rhinoscopy
  • Nasal endoscopy
  • CT when appropriate

When Is a CT Scan Needed for Sinusitis?

CT is not routinely required for every episode of acute sinusitis.

A CT scan of the paranasal sinuses may be appropriate:

  • To objectively assess suspected chronic rhinosinusitis
  • For anatomical assessment before sinus surgery
  • When a complication is suspected
  • When an alternative diagnosis is being considered

Mucosal changes seen on CT should always be interpreted alongside symptoms and clinical examination.

How Is Acute Sinusitis Treated?

Most acute viral rhinosinusitis improves without specific antimicrobial treatment.

Appropriate symptomatic treatment may include:

  • Analgesics for pain or fever
  • Saline nasal irrigation
  • Topical intranasal corticosteroids

Topical nasal decongestants may provide short-term relief in selected patients but should not be used for prolonged periods because rebound nasal congestion can occur.

Antihistamines may be useful when allergic rhinitis is also present but are not routinely required for every episode of acute sinusitis.

When Are Antibiotics Needed for Sinusitis?

Antibiotics are not needed for every case of sinusitis. Most acute rhinosinusitis is viral.

Even in uncomplicated acute bacterial rhinosinusitis, watchful waiting can be appropriate for selected adults when reliable follow-up is available.

When antibiotic treatment is chosen, the decision should consider:

  • Age
  • Drug allergies
  • Other medical conditions
  • Previous antibiotic exposure
  • Clinical severity

The 2025 adult sinusitis guideline recommends amoxicillin with or without clavulanate as first-line therapy for most adults when antibiotic treatment is selected, generally for 5–7 days.

Antibiotics should not be self-started. Unnecessary antibiotic use can cause adverse effects and contribute to antimicrobial resistance.

How Is Chronic Sinusitis Treated?

The aim of chronic rhinosinusitis treatment is to control persistent sinonasal inflammation and improve nasal function and quality of life.

Core treatments include:

  • Saline nasal irrigation
  • Topical intranasal corticosteroids

Associated conditions such as allergy or asthma should also be managed when relevant.

The presence or absence of nasal polyps should be documented. In selected patients with severe chronic rhinosinusitis with nasal polyps that remains uncontrolled despite appropriate medical and/or surgical management, biological therapies may also be considered.

Chronic sinusitis should not be viewed simply as an infection requiring months of antibiotics. Routine antimicrobial therapy is not recommended for chronic rhinosinusitis without an acute exacerbation.

When Is Sinus Surgery Considered?

Not every patient with chronic rhinosinusitis requires surgery.

Endoscopic sinus surgery may be considered for appropriately selected patients with confirmed chronic rhinosinusitis whose symptoms remain clinically significant.

Decision-making may consider:

  • Severity and duration of symptoms
  • Nasal endoscopy findings
  • CT findings
  • Presence of nasal polyps
  • Previous medical treatment
  • Impact on quality of life
  • Patient preferences

The aim of endoscopic sinus surgery is to improve sinus ventilation and drainage and to allow topical treatments to reach affected areas more effectively.

Because chronic rhinosinusitis is an inflammatory condition, saline irrigation, topical medication and ongoing follow-up may still be required after surgery.

How to Perform Nasal Irrigation Safely

Saline nasal irrigation may help relieve symptoms in both acute and chronic rhinosinusitis.

The water used for irrigation must be safe.

Do not use water directly from the tap for nasal irrigation. Use distilled or sterile water, or tap water that has been properly boiled and allowed to cool. Nasal-rinsing devices should also be cleaned and dried according to the manufacturer's instructions.

Commercially prepared sterile saline products can also be used.

When Should You See a Doctor for Sinusitis?

Medical assessment is appropriate if:

  • Symptoms last longer than 10 days without improvement
  • Symptoms improve and then become worse again
  • There is severe facial pain or headache
  • Fever is prolonged or severe
  • There are repeated sinus infections during the year
  • Nasal obstruction, discharge or reduced smell lasts longer than 12 weeks
  • Significant symptoms persist despite treatment

Marked swelling or redness around the eye, reduced or double vision, a very severe headache, altered consciousness or neck stiffness may require urgent medical assessment.

Have Your Sinus Symptoms Assessed

Persistent nasal obstruction, postnasal drainage, facial pressure or loss of smell can be assessed for acute and chronic rhinosinusitis and other possible causes.

Frequently Asked Questions

What is sinusitis?
Sinusitis or rhinosinusitis is inflammation of the paranasal sinuses around the nose and usually the nasal lining as well. It can cause nasal obstruction, nasal or postnasal discharge, facial pain or pressure and a reduced sense of smell.
Does yellow or green nasal mucus mean bacterial sinusitis?
No. Yellow or green nasal mucus can also occur with viral infections. Bacterial rhinosinusitis becomes more likely when symptoms continue for 10 days or longer without improvement or when they initially improve and then worsen again.
Can going outside with wet hair cause sinusitis?
Going outside with wet hair or exposure to cold weather is not considered a direct cause of sinusitis. Viral upper respiratory infections are the most common cause of acute sinusitis. Allergy, tobacco smoke, nasal polyps and some chronic medical conditions may also increase risk.
Are antibiotics necessary for sinusitis?
Antibiotics are not required for every case of sinusitis. Most acute rhinosinusitis is viral. The decision to prescribe antibiotics should consider symptom duration, whether symptoms worsened after initial improvement, the patient's clinical condition and the risk of complications.
How long does chronic sinusitis last?
Chronic rhinosinusitis is assessed when relevant sinonasal symptoms last for more than 12 weeks and sinonasal inflammation is objectively documented by examination, nasal endoscopy or CT when appropriate.
Is a CT scan always required to diagnose sinusitis?
No. Routine CT or other radiological imaging is not recommended for uncomplicated acute rhinosinusitis. CT can be used to objectively assess chronic rhinosinusitis, for surgical planning, or when a complication or alternative diagnosis is suspected.
Does surgery permanently cure chronic sinusitis?
Endoscopic sinus surgery can significantly improve symptoms and quality of life in appropriately selected patients, but chronic rhinosinusitis is a long-term inflammatory condition. Saline irrigation, intranasal medication and ongoing follow-up may still be required after surgery.
Can tap water be used for nasal irrigation?
Water directly from the tap should not be used for nasal irrigation. Use distilled or sterile water, or tap water that has been properly boiled and allowed to cool. Nasal-rinsing devices should also be cleaned and dried according to the manufacturer's instructions.
Academic Hospital note: Treatment of sinusitis depends on symptom duration, the likelihood of viral or bacterial disease, chronic inflammation and the presence of nasal polyps. Persistent or recurrent symptoms may require ENT assessment. You can book an appointment.

References

  1. Academic Hospital. What Is Sinusitis? What Are Its Symptoms and Treatment Methods?
  2. American Academy of Otolaryngology–Head and Neck Surgery Foundation. Clinical Practice Guideline: Adult Sinusitis Update – 2025
  3. American Academy of Otolaryngology–Head and Neck Surgery Foundation. Clinical Practice Guideline: Surgical Management of Chronic Rhinosinusitis – 2025
  4. Centers for Disease Control and Prevention. Sinus Infection Basics
  5. Centers for Disease Control and Prevention. How to Safely Rinse Sinuses