A stye, also known as a hordeolum, is a bacterial infection of an oil gland in the eyelid. This results in a red tender bump at the edge of the eyelid. The outside or the inside of the eyelid can be affected. The cause of a stye is usually a bacterial infection by Staphylococcus aureus. The internal ones are due to infection of the meibomian gland while the external ones are due to an infection of the gland of Zeis. A chalazion on the other hand is a blocked oil gland without infection. A chalazion is typically in the middle of the eyelid and not painful. Often a stye will go away without any specific treatment in a few days or weeks. Recommendations to speed improvement include warm compresses. Occasionally antibiotic eye ointment may be recommended. While these measures are often recommended, there is little evidence for use in internal styes. The frequency at which styes occur is unclear, though they may occur at any age. Signs and symptoms The first sign of a stye is a small, yellowish spot at the center of the bump that develops as pus and expands in the area. Other stye symptoms may include: A lump on the top or bottom eyelid Localized swelling of the eyelid Localized pain Redness Tenderness Crusting of the eyelid margins Burning in the eye Droopiness of the eyelid Scratchy sensation on the eyeball (itching) Blurred vision Mucous discharge in the eye Irritation of the eye Light sensitivity Tearing Discomfort during blinking Sensation of a foreign body in the eye Complications Stye complications occur in very rare cases. However, the most frequent complication of styes is progression to a chalazion that causes cosmetic deformity, corneal irritation, and often requires surgical removal. Complications may also arise from the improper surgical lancing, and mainly consist of disruption of lash growth, lid deformity or lid fistula. Large styes may interfere with one's vision. Eyelid cellulitis is another potential complication of eye styes, which is a generalized infection of the eyelid. Progression of a stye to a systemic infection (spreading throughout the body) is extremely rare, and only a few instances of such spread have been recorded. Cause A stye is caused by a bacterial infection. The bacteria are Staphylococcus aureus in about 95% of cases. The infection leads to the blocking of an oil gland at the base of the eyelash. Styes