The complications from untreated sinusitis in a 10-month-old male infant, though at the more severe end of the spectrum, brings to light the importance of diagnosis and treatment even in the very young patient. Acute sinusitis should be diagnosed using established guidelines. Appropriate pharmacologic and osteopathic manipulative treatment should be initiated on diagnosis. Initial antibiotic therapy is a 14-day course of amoxicillin. If the sinusitis fails to resolve, a trial of a second-line antibiotic should be considered. The use of adjunctive medications such as antihistamines, decongestants, and nasal steroids remains controversial. If the patient fails maximal medical therapy, a computed tomography scan and referral to an otolaryngologist for possible surgical intervention should be considered.