A chalazion is a small tumor of the upper or lower eyelid of inflammatory origin, due to the obstruction of a palpebral gland, the Meibomian gland. It can affect children or adults at any age.
It is sometimes more common in diabetic patients, but some non-diabetic people can have them repeatedly.
The chalazion is generally not very painful, but it can become superinfected, becoming very inflamed, painful and giving the eyelid a red and swollen appearance.
Treatment consists of the rapid application of eye drops and antibiotic and anti-inflammatory ointments but sometimes surgical treatment is necessary (simple incision inside the eyelid after local anesthesia).
The chalazion is benign but its recurring nature can become exasperating for the patient.
It is distinguished from a stye which corresponds to the infection of the hair follicle of an eyelash, which is generally closer to the outer edge of the eyelid, often with a small white head that never requires an incision but also heals with ointments.