Bloodshot describes eyes that look red because tiny blood vessels near the surface have become swollen and visible. When you look at someone with bloodshot eyes, you can see red lines or patches spreading across the white parts of their eyes, making them look pink or even bright red.

Eyes become bloodshot for many reasons. Staying up too late studying or reading can make eyes bloodshot because they get tired and strained. Rubbing your eyes too hard can irritate them and cause redness. Swimming in a chlorinated pool often leaves eyes temporarily bloodshot. Crying makes eyes bloodshot too. Sometimes allergies, dust, or being sick with a cold can cause the redness.

While bloodshot eyes might look alarming, they're usually harmless and go away with rest. When someone has bloodshot eyes, it's often a sign they need sleep or need to rest their eyes from screens or books.