Air exiting the eye when blowing the nose is a peculiar experience resulting from pressure dynamics within the head. This startling occurrence reveals a direct connection between the nasal cavity and the eye. While tears normally flow one way, a forceful expulsion of air can temporarily reverse this natural drainage path. Understanding the anatomy of the tear system and nasal pressure explains this unusual event.
The Anatomical Connection
The connection allowing air to pass from the nose to the eye is the nasolacrimal system, the body’s built-in tear drainage apparatus. Tears lubricate the eye and collect toward the inner corner, where they enter tiny openings called puncta. These puncta are located on the margins of the upper and lower eyelids.
Tears flow through small tubes called canaliculi into the lacrimal sac, which is nestled beside the nose. The sac narrows into the nasolacrimal duct, a channel that runs downward through a bony canal and opens into the nasal cavity. This pathway carries fluid away from the eye and into the nose, explaining why crying often causes a runny nose. The duct’s opening into the nose is typically covered by a fold of tissue, such as the valve of Hasner. This tissue acts like a check valve to prevent air or mucus from traveling backward.
How Nasal Pressure Forces Air Out
Blowing the nose, especially by blocking both nostrils, creates a sudden and significant increase in air pressure within the nasal cavity and associated sinuses. This forceful spike in pressure is often enough to overcome the normal function of mucosal folds, like the valve of Hasner, that usually prevent backflow.
This excess air pressure forces its way backward up the nasolacrimal duct, through the lacrimal sac, and into the canaliculi. The air is finally expelled through the puncta, appearing to come out of the eye itself. This reverse flow is more likely in individuals with naturally wider tear ducts or an incompetent valve of Rosenmüller, located where the canaliculi meet the lacrimal sac. The air expulsion is a temporary pressure release and is generally harmless if it is the only symptom present.
When to Seek Medical Attention
The occasional escape of air through the eye when blowing the nose, without other symptoms, is typically a benign anatomical quirk. However, this phenomenon can signal a more serious underlying issue, especially following facial trauma. Immediate medical attention is necessary if air exits the eye accompanied by new pain, noticeable swelling, or changes in vision.
A forceful increase in nasal pressure can sometimes force air through a fracture in the thin bony walls separating the nasal cavity from the eye socket. This condition is known as orbital emphysema, where air collects in the tissues around the eye, causing swelling and possible vision impairment. If the air escape began after a fall or impact to the face, it may indicate an orbital fracture. Professional assessment is required to prevent complications like infection or muscle entrapment. Following facial trauma, patients are often instructed to avoid blowing their nose entirely to prevent air from worsening swelling.