A 4 year-old boy presents with purulent, foul-smelling nasal discharge for three days. The exam shows unilateral nasal discharge with a bright reflection of light. Which is the most likely diagnosis?

• A. Viral URI
• B. Acute sinusitis
• C. Allergic rhinitis
• D. Nasal foreign body

Answer: (D)

Unilateral foul-smelling nasal discharge in a young child strongly points to a nasal foreign body. When an object blocks one nostril, it creates pooling and bacterial growth in that side, leading to a persistent, malodorous, purulent discharge. Other conditions tend to affect both sides or show different features: viral upper respiratory infections usually cause bilateral symptoms with non-foul mucus and often mild fever; allergic rhinitis presents with itchy eyes and nose, sneezing, and bilateral, clear to mucoid discharge without a foul odor; acute sinusitis can yield purulent discharge but is typically accompanied by facial pain or pressure and fever, and may follow a viral illness. The unilateral, odiferous discharge in this age group makes a nasal foreign body the most likely diagnosis.