Properly termed hordeolum, a sty is a localized infection of various glands in the eyelid. Those that are associated with the glands of the lashes are called external hordeolum and those associated with the oil or meibomian glands are called internal hordeolum." The most common cause of hordeolum is infection caused by staph. bacteria. However, unless there is associated discharge from the area, a hordeolum is not typically contagious.

Hordeolum generally appear as local areas of redness and elevation or swelling of the eyelid. In some cases there can be a "white-head" to the area or a pustule. The area is typically tender and irritated. It will be especially tender or even painful to touch. Hordeolum will form when the lid glands are obstructed with dirt or debris. This allows for normally present bacteria of the lid to multiply within the gland and for the area to become infected. Occasionally a hordeolum can result in a spread of infection which leads to a much greater degree of eyelid swelling, pain, and redness known as preseptal cellulitis.

Treatment for a hordeolum includes hot compresses to the area, the use of topical antibiotic or antibiotic/steroid combination ointments, oral antibiotics, and drainage of the hordeolum. If a secondary preseptal cellulitis develops then oral antibiotics are always required.