A sty (sometimes spelled stye) is a tender, painful red bump located at the base of an eyelash or inside the eyelid. A sty results from an acute infection of the oil glands of the eyelid that occurs after these glands have become clogged. A sty also may arise from an infected hair follicle at the base of an eyelash. Symptoms are generally redness, tenderness, and pain in the affected area. The eye may feel irritated or "scratchy." Later symptoms can include swelling, discomfort during blinking, watering of the eye, and light sensitivity. A common sign of a sty is a small, yellowish spot at the center of the bump that develops as pus expands in the area. People of all ages and both genders can develop a sty. Application of a warm compress or washcloth to the affected area for 10 minutes, four to six times a day, can speed rupture of the sty and aid in the relief of symptoms. A sty should not be pressed or squeezed to facilitate drainage. If a sty persists for several days, a doctor may lance (drain) the infection under local anesthesia.