A chalazion /kəˈleˌzi.ən/ (plural chalazia /kəˈleˌzi.ə/), also known as a meibomian gland lipogranuloma, is a cyst in the eyelid that is caused by inflammation of the meibomian gland, usually on the upper eyelid. Chalazions differ from styes (hordeolums) in that they are usually painless apart from the tenderness caused when they swell up. A chalazion may eventually disappear on its own after a few months, though more often than not, some treatment is necessary.