A chalazion (; plural chalazia or chalazions) or meibomian cyst is a cyst in the eyelid usually due to a blocked meibomian gland, typically in the middle of the eyelid, red, and not painful. They tend to come on gradually over a few weeks.
A chalazion may occur following a stye or from hardened oils blocking the gland. The blocked gland is usually the meibomian gland, but can also be the gland of Zeis.
A stye and cellulitis may appear similar. A stye, however, is usually more sudden in onset, painful, and occurs at the edge of the eyelid. Cellulitis is also typically painful.
Treatment is initiated with warm compresses. In addition, antibiotic/corticosteroid eyedrops or ointment may be used. If this is not effective, injecting corticosteroids into the lesion may be tried. If large, incision and drainage may be recommended. While relatively common, the frequency of the condition is unknown. It is most common in people 30–50 years of age, and equally common in males and females. The term is from the Greek khalazion (χαλάζιον) meaning "small hailstone".