A red eye is usually nothing to worry about and often gets better on its own. But sometimes it can be more serious and you'll need to get medical help.
Lots of different things can cause a red eye.
Your symptoms might give you an idea of what's causing it.
If your eye does not hurt and your sight is not affected, it's probably nothing serious. It may get better on its own in a few days.
Until it has got better:
If your GP cannot find what's causing your red eye, they may refer you to an eye specialist (ophthalmologist) for tests.