What causes a chalazion?
The narrow opening through which a meibomian gland secretes its material can become clogged from narrowing of the opening or hardening of the sebaceous liquid near the opening. If this occurs, the gland will have a backup of the material it secretes and the obstructed gland will swell. This leads to thickening of the walls of the gland and leakage of oil into the lid itself, causing inflammation both within the gland and the eyelid. This inflamed enlargement is a chalazion.