Why do some people experience red eyes and how can they clear them?

Red eyes just mean that the outer layer of the eye is inflamed. It could be inflamed because there's serious inflammation deeper inside the eye, such as certain types of immune diseases that can affect the eyes. They could be red because of hormonal diseases, such as thyroid disease that causes inflammation of the muscles around the eye. They could be red simply because you stayed up too late the night before and didn't get enough sleep, or your eyelids don't close all the way when you sleep at night, or you don't drink enough water, or you had too much caffeine. The specific root cause will determine what the treatment should be. For people who are feeling a bit of garden-variety red eye, the best thing to do is to get artificial teardrops over the counter that are preservative free. You can use those one or two times a day. If you're using it more than a couple of times a day, then there's something more significant going on that warrants being examined.