Chinese Association of Idaho State University (CAISU)
Their surface is covered in blood vessels that expand when they’re irritated or infected. That gives your eyes the red look. Eyestrain can do it, and so can a late night, a lack of sleep, or allergies. If an injury is the cause, get it checked by your doctor. Red eyes could be a symptom of another eye condition, like conjunctivitis(pinkeye) or sun damage from not wearing shades over the years.