A stye is an acute infection of the secretory glands of the eyelids. This common infection results from blocked glands within the eyelid. When the gland is blocked, the oil produced by the gland occasionally backs up and extrudes through the wall of the gland, forming a lump (chalazion), which can be red, painful, and nodular. Frequently, bacteria can infect the blocked gland, causing increased inflammation, pain, and redness of the eye, and even redness of the surrounding eyelid and cheek tissue. The medical term for stye is hordeolum.