麦粒肿，又称偷针眼 或 针眼，是一种在睫毛底部皮脂腺的感染。虽然它们不会造成永久性的伤害，但是它们会使人非常疼痛。

麦粒肿通常是由于金黄色葡萄球菌感染所致。虽然麦粒肿经常在青少年时期出现，然而在人生的其他阶段也时有发生。麦粒肿可以由压力和营养不良所引起。使用同一把刮过胡子的剃刀刮眼睛周围的头发很可能会扩散金黄色葡萄球菌，为得上麦粒肿或其他眼睛感染疾病提供潜在的危险。金黄色葡萄球菌具有传染性，所以要注意避免用手揉眼睛，与别人共用毛巾和浴巾。麦粒肿一般会持续1周至3周之内。

An external stye or sty /ˈstaɪ/, also hordeolum /hɔːrˈdiːələm/, is an infection of the sebaceous glands of Zeis at the base of the eyelashes, or an infection of the apocrine sweat glands of Moll. External styes form on the outside of the lids and can be seen as small red bumps. Internal styes are infections of the meibomian sebaceous glands lining the inside of the eyelids. They also cause a red bump underneath the lid with only generalized redness and swelling visible on the outside. Styes are similar to chalazia, but they tend to be smaller and more painful, and they usually don't cause any lasting damage. They contain water and pus, and the bacteria will spread if the stye is forcefully ruptured. Styes are characterized by an acute onset and usually short in duration (7–10 days without treatment) compared to chalazia, which are chronic and usually do not resolve without intervention. Styes are usually caused by the Staphylococcus aureus bacterium.