Hordeolum is a common, painful, inflammation of the eyelid margin that is usually caused by bacterial infection. The infection affects oil glands of the eyelid and can be internal or external. In many cases, the lesion drains spontaneously and resolves untreated; however, the inflammation can spread to other ocular glands or tissues and recurrences are common. If unresolved, acute internal hordeolum can become chronic or develop into a chalazion. External hordeola, also known as styes, were not included in the scope of this review.