Acute Sinusitis in Children

Prepared and reviewed by the PrepElephant Academic Review Team

First published 14 Oct 2026 · Spot an error?

Reference basis: Nelson Textbook of Pediatrics; Ghai Essential Pediatrics; AAP Clinical Practice Guideline on Acute Bacterial Rhinosinusitis

On this page

Direct answer
What you must remember
Viral or bacterial: reading the clinical course
Where the exam tries to catch you
Frequently asked questions
Related topics

Direct answer

Acute sinusitis in children is inflammation of the paranasal sinuses lasting up to four weeks, most often following a viral upper respiratory infection. Bacterial infection is suspected when symptoms persist beyond ten days without improvement, or when a severe onset with high fever and purulent discharge occurs. The diagnosis is clinical, antibiotics are reserved for bacterial criteria, and orbital complications need urgent review.

What you must remember

Duration: acute rhinosinusitis lasts up to four weeks, and most cases are viral, with symptoms beyond ten days raising suspicion of bacterial infection.
Bacterial criteria: persistent symptoms beyond ten days, a severe onset with fever of about 39 degrees Celsius and purulent discharge for three or more days, or double worsening after initial improvement.
Organisms: Streptococcus pneumoniae, nontypeable Haemophilus influenzae and Moraxella catarrhalis, the same organisms behind acute otitis media.
Sinus development: ethmoid and maxillary sinuses are present at birth, while the frontal and sphenoid sinuses develop later, so frontal sinusitis is uncommon in toddlers.
Imaging: not needed for routine diagnosis, because plain radiographs are unreliable and CT is reserved for complications or treatment failure.
Antibiotics: amoxicillin, or amoxicillin-clavulanate in many settings, for confirmed bacterial disease, with watchful waiting for uncomplicated viral illness.
Complications: orbital cellulitis, subperiosteal abscess, intracranial infection and cavernous sinus thrombosis.

Viral or bacterial: reading the clinical course

A 6-year-old has a blocked nose and thick discharge for nine days, with mild fever that has begun to ease. The table separates the two courses, which is the key skill on this topic.

Feature	Likely viral	Likely bacterial
Duration	Under ten days and improving	Beyond ten days without improvement
Onset	Gradual, mild	Severe, with high fever
Fever	Low to moderate, easing	Persistent or high
Pattern	Steady improvement	Double worsening after initial recovery
Management	Symptomatic care	Antibiotics, usually amoxicillin-based

Discharge colour alone is unreliable, because viral infection also produces thick green secretions. Duration, severity and the pattern of change decide whether antibiotics are justified.

Children with a clear viral course need reassurance, nasal saline and analgesia, with a review date if symptoms change. Those with bacterial features need a defined antibiotic plan and early review, so that treatment failure is picked up before complications develop. Parents should be told which warning signs, such as periorbital swelling, severe headache or drowsiness, need same-day assessment, because these mark the complications the exam expects you to recognise.

Where the exam tries to catch you

Three mistakes recur on this topic.

Trap: starting antibiotics for any green nasal discharge Correct: purulent discharge occurs in viral infection too, so duration and severity decide.
Trap: ordering a routine sinus radiograph to confirm the diagnosis Correct: the diagnosis is clinical, and imaging is reserved for suspected complications or treatment failure.
Trap: missing orbital involvement in a child with sinusitis Correct: periorbital swelling, proptosis, pain on eye movement or reduced vision need urgent imaging and IV antibiotics.

Frequently asked questions

What duration of symptoms suggests bacterial sinusitis in children?

Symptoms that persist beyond ten days without improvement suggest bacterial acute sinusitis in children. A severe onset with high fever and purulent nasal discharge for three or more days, or symptoms that improve and then worsen again, are also accepted triggers for antibiotics.

Is an X-ray needed to diagnose acute sinusitis in children?

An X-ray is not needed to diagnose acute sinusitis in children, because the diagnosis is clinical. Plain radiographs are unreliable, and CT is reserved for suspected orbital or intracranial complications or for treatment failure.

Which organisms cause bacterial acute sinusitis in children?

Streptococcus pneumoniae, nontypeable Haemophilus influenzae and Moraxella catarrhalis cause most bacterial acute sinusitis in children. These are the same organisms behind acute otitis media, which is why amoxicillin-based therapy is first-line.

Which complication of acute sinusitis is most dangerous?

Orbital cellulitis and intracranial spread are the most dangerous complications of acute sinusitis in children, and the ethmoid sinus is the commonest source of orbital infection. Periorbital swelling, proptosis, ophthalmoplegia or reduced vision signal an emergency needing urgent imaging and IV antibiotics.