13 Causes of Red Eye

3. Stye

A stye is a painful growth near the eyelid, and it can form on the inner or the outer part of the eyelid. The sty usually causes irritation and pain in the eye and can lead to redness of the eye. According to the Mayo Clinic, styes are usually caused by an infection of oil glands in the eyelid, from the bacterium Staphylococcus. People who are not careful to wash their hands before touching their eyes, people who leave makeup on overnight, and those who use expired or unhygienic makeup products are at greater risk for developing a stye. In most cases, the stye resolves on its own within a few days. If the eye becomes inflamed or if the symptoms do not subside, make an appointment with your general practitioner, who may refer you to an ophthalmologist for treatment.