Most cases of red eyes are caused by minor eye conditions typically, however, in cases where red eyes are causing you pain, it may be due to something more severe.
Conjunctivitis often cause painless red eyes. Also referred to as pink eye, conjunctivitis is an eye infection that arises after the conjunctiva in your eyes have become inflamed due to infection, an allergic reaction or a response to an irritant.
Dry eye syndrome can sometimes cause eyes to redden due to their lack of moisture. Over the counter eye drops, used to rehydrate eyes and ease discomfort and irritation can treat red eye. Both conjunctivitis and dry eye are eye problems that can also cause your eyes to be sensitive to light
Burst blood vessels also cause the appearance of red or bloodshot eyes. Tiny blood vessels can burst as a result of straining or coughing severely and appear as red blotches on the surface of your eye. However, these are not usually anything to worry about and will disappear within a couple of weeks.
Other causes of red eye include blepharitis, ingrowing eyelashes and eyelid problems.
If your red eyes are causing much pain, this could be down to a more serious eye condition such as uveitis or glaucoma or could be the result of a corneal ulcer or scratch.
These conditions can be harmful to your eyes and sight and should be identified and treated by an optician or GP as soon as possible. Glaucoma, in particular, can pose a more serious threat to your vision if not treated quickly. Blurred vision often accompanies it.