Blepharitis (blef-uh-RYE-tis) is a condition that causes swelling, itching and other irritation of the eyelids. Blepharitis usually affects both eyes along the edges of the eyelids. Blepharitis may be caused by usually harmless bacteria on eyelids that become overpopulated. Another common cause is clogged oil glands of the eyelid. Other diseases or conditions may play a role in blepharitis or make it more likely to occur. Blepharitis can't be cured, but daily care and treatments can usually control the symptoms. Blepharitis can be uncomfortable, but it usually doesn't cause permanent damage to your eyesight. It can't be passed from one person to another.