What are the causes for Chalazion (Lump in Eyelid)?

Each of the oil glands, called meibomian glands, produces oil that flows out of the gland into the tears. The oil exits from each gland through a tiny circular opening just behind the eyelashes of the upper and lower lids of both eyes. A chalazion is caused by the oil in the gland becoming too thick to flow out of the gland or the opening of the gland being obstructed. Without anywhere to go, the oil builds up inside the gland and forms a lump in the eyelid. The gland wall may break, releasing the oil into the tissue of the eyelid, causing inflammation and sometimes scar tissue. Alternative names for a chalazion include conjunctival granuloma, conjunctival lipogranuloma, or meibomian gland lipogranuloma.

Source: http://www.emedicinehealth.com