A chalazion is a small bump in the eyelid caused by a blockage of the tiny oil glands.

Causes

A chalazion is caused by a blocked duct in one of the meibomian glands. These glands are located in the eyelid directly behind the eyelashes. They produce a thin, oily fluid that lubricates the eye.

Symptoms

A chalazion often develops following an internal hordeolum (also called a stye). The eyelid most often becomes tender, red, swollen, and warm. Sometimes, the blocked gland causing the stye will not drain even though the redness and swelling go away. The gland will form a firm nodule in the eyelid that is not tender. This is called a chalazion.