The most common cause of a blocked tear duct is the failure of the thin tissue, or membrane, that covers the tear duct (lacrimal duct) to open normally into the nasal passage shortly after birth. This disrupts the usual drainage system for tears.

Symptoms usually are not noticed if the blockage resolves on its own before a baby starts producing tears. Normally, tears start forming within the first few days to weeks following birth.

Less common causes of blocked tear ducts in babies can include:

• Infection in the tubes that drain tears from the eyes to the nose (dacryocystitis).
• Blockage of the tear duct at both ends (dacryocystocele).
• Abnormal growth of the nasal bone that puts pressure on a tear duct, closing it off.
• Closed or undeveloped openings in the corners of the eyes (puncta) where tears normally drain into the tear ducts.

Blocked tear ducts in adults

The cause of blocked tear ducts in adults is usually related to another disorder or an injury. For example, a blocked tear duct may result from a thickening of the tear duct lining, abnormal tissue or structures in the nose, or complications of surgery on or around the nose. These types of problems are more likely to occur after age 60.