Red eye is a common ailment that can affect one or both eyes. Your eyes get red due to the expansion of the tiny blood vessels on the surface of the eyes. It can occur due to an injury, illness, eye infections, or other condition such as allergies. Red eye does not usually require medical attention and can be cured using over the counter eye drops or home remedies, but it may require immediate attention if you experience symptoms such as- the inability to open eyes, change in vision, nausea or vomiting, severe headache or pain in eyes, unusual sensitivity to light, foreign object in your eye, sudden halos around light, and swelling in the eyes.