1. OVERVIEW

Acute rhinosinusitis is a condition caused by infection of one or more of the paranasal sinuses. Viral infections associated with the common cold are the most common cause of acute rhinosinusitis, commonly referred to as viral rhinosinusitis.

Uncomplicated viral rhinosinusitis usually resolves spontaneously within 7 to 10 days without treatment. Although acute bacterial rhinosinusitis (ABRS) may also resolve without treatment, antibiotic therapy can help accelerate recovery.

1. ANATOMY

Paranasal Sinus Anatomy

The diagram illustrates the location of the frontal sinuses, ethmoid sinuses, maxillary sinuses, and sphenoid sinuses.

Sinuses are hollow cavities within the facial bones. They are lined with a thin mucosal layer that normally produces a small amount of mucus. When this lining becomes irritated or infected, it swells and produces more mucus, leading to symptoms.

The timing and development of the paranasal sinuses vary depending on anatomical location. In most individuals, the nasal cavity and paranasal sinuses reach near-adult size by around 12 years of age, although complete development may not occur until about 20 years of age.

• Maxillary sinuses are present at birth and grow rapidly around the age of four. Ciliary activity is essential to drain secretions from the maxillary sinus into the nasal cavity because the drainage openings are located high on the medial wall.

• Ethmoid sinuses are also present at birth. They consist of multiple small air cells, each with its own drainage opening into the nasal cavity.

• Sphenoid sinuses begin developing during the first two years of life, are typically fully aerated by about 5 years of age, and reach their fixed size around 12 years of age.

• Frontal sinuses develop later and show significant variation. They can be distinguished from the ethmoid sinuses on X-ray between 6 and 8 years of age. In children, frontal sinuses begin forming around 7–8 years of age (some sources report around 9 years) and continue to develop until approximately 19–20 years of age.

2. DEFINITION

Acute bacterial rhinosinusitis (ABRS) occurs when a secondary bacterial infection develops in the sinuses.

The condition is classified based on duration and recurrence:

Acute

Symptoms resolve completely within < 30 days.

Subacute

Symptoms resolve completely within ≥ 30 days but < 90 days.

Recurrent acute

• At least three episodes lasting < 30 days, separated by ≥ 10 symptom-free days within six months, or

• At least four episodes within 12 months
  Individual episodes respond quickly to antibiotic therapy.

Chronic sinusitis

Chronic sinusitis is defined as paranasal sinus inflammation lasting more than 90 days, with persistent symptoms such as:

• cough

• runny nose

• nasal congestion

Chronic sinusitis may be associated with non-infectious conditions, including:

• allergies

• cystic fibrosis

• ciliary dysfunction

• gastroesophageal reflux disease (GERD)

• exposure to environmental pollutants

3. EPIDEMIOLOGY

Acute bacterial rhinosinusitis is common in children.

Approximately 6–9% of viral upper respiratory infections in children are complicated by secondary acute bacterial sinusitis.

In children, ABRS most commonly occurs between the ages of 4 and 7, although it can occur at any age, including in infants. Complications from ethmoid sinusitis may occasionally be observed in infants.

ABRS is less common in children under two years of age compared with older children.

4. SYMPTOMS OF SINUSITIS

Common symptoms include:

• Cough

• Nasal congestion

• Runny nose

• Fever

• Headache

• Facial pain or swelling

• Sore throat

• Bad breath

In most cases, symptoms begin to improve within 7–10 days.

5. IMAGING STUDIES

Imaging tests are usually not necessary in evaluating children with uncomplicated acute bacterial sinusitis.

If imaging studies are performed (X-ray, CT scan, or MRI), abnormal findings should always be interpreted in conjunction with clinical symptoms and physical examination.

However, imaging abnormalities cannot reliably distinguish between bacterial sinusitis, viral sinusitis, or other causes.

6. DIAGNOSIS

Uncomplicated acute bacterial rhinosinusitis

Diagnosis of uncomplicated ABRS in children is usually clinical.

Imaging studies are not recommended for routine diagnosis.

Diagnosis is based on:

● Symptoms consistent with sinusitis
(daytime cough, nasal symptoms, or both)

● Clinical patterns suggesting bacterial infection rather than viral infection, including:

• Symptoms persisting >10 days but <30 days without improvement, or

• Severe symptoms (ill appearance, temperature ≥39°C / 102.2°F, and purulent nasal discharge for ≥3 consecutive days), or

• Worsening symptoms (increasing respiratory symptoms, new severe headache or fever, or recurrent fever after initial improvement)

Complicated acute bacterial sinusitis

Imaging studies are usually performed when complications are suspected.

7. HOW CAN YOU HELP YOUR CHILD FEEL BETTER?

To help relieve your child’s symptoms, you can:

● Give pain relievers such as acetaminophen (Hapacol, Efferalgan, Tylenol)

● Rinse your child’s nose and sinuses with saline solution several times per day

● Ensure your child drinks plenty of fluids. Adequate hydration helps thin mucus and promotes drainage.

8. WHEN SHOULD YOU SEE A DOCTOR?

See a doctor if your child has:

• Nasal congestion or runny nose lasting more than 10 days without improvement

• Fever higher than 38°C (100.4°F) or yellow/green nasal discharge lasting 3–4 consecutive days

• Symptoms that initially improve but then worsen again

Sometimes sinusitis can lead to serious complications.

Seek medical care immediately if your child has:

● Fever higher than 39°C (102.2°F)
● Facial pain or headache
● Swelling or redness around one or both eyes
● Neck stiffness

Go to the emergency department immediately if your child has:

● Sudden severe pain in the face or head
● Difficulty seeing or double vision
● Confusion or difficulty thinking clearly
● Difficulty breathing

Source:
UpToDate 2026
Acute bacterial rhinosinusitis in children: Clinical features and diagnosis
Patient education: Sinusitis in children (The Basics)