Pneumocephalus is defined as the abnormal presence of air in the intracranial cavity. Pneumocephalus is most commonly caused by trauma, but there are rare reports of pneumocephalus secondary to allergy-induced sinusitis. In this report, we present a woman in her 60s who presented to the emergency department with a chief complaint of headache after experiencing a ‘popping’ sensation in her ears while sneezing. Over the course of a day, she began experiencing severe pain across the forehead along with copious amounts of clear rhinorrhea. A head CT without contrast was ordered, and findings revealed large amounts of intracranial air visualised diffusely throughout the subarachnoid spaces and the anterior horn of the left lateral ventricle. A diagnosis of pneumocephalus was confirmed. This patient made a full recovery without surgical intervention. Standard conservative therapy included bed rest, head elevation, avoidance of activities that increase intracranial pressure and antibiotic prophylaxis for meningitis.