What red eyes are and why they happen
An eye turns red when tiny blood vessels on the white of the eye or inside the eyelid widen. The body reacts this way to irritation, inflammation, allergy, infection or injury, so redness alone says little about the cause. What comes with it matters more: pain, discharge, itching, blurred vision, sensitivity to light. These signs show how urgent a visit is. A diagnosis cannot be made from a text.
Red eyes with discharge and eyelids stuck together
The most common cause is conjunctivitis, inflammation of the outer lining of the eye. With a viral infection the discharge is watery, it often starts in one eye and moves to the other, and it sometimes comes with a cold. With a bacterial infection the discharge is sticky, yellowish or greenish, and the lids may be stuck shut in the morning. Both forms are contagious: wash your hands often, use your own towel and do not rub your eyes. If red eyes come with a sticky discharge, see an eye doctor or a general practitioner.
Red eyes with itching and watering
With an allergy, both eyes usually turn red, itch and water, the lids may swell, and you may sneeze or have a runny nose. It often follows the pollen season, dust or contact with animals. Read more on the Allergy page. If you suspect an allergy, see an eye doctor or an allergist, and for a runny nose see Runny nose.
Dry and tired eyes
Long screen work, air conditioning, dry air and contact lenses dry out the surface of the eye: burning, a gritty feeling and redness by evening. Blink more often, take breaks from the screen and air out the room. If the symptoms do not go away or keep returning, have your eyes checked.
Red eyes in a child
In children it is again most often conjunctivitis, and it spreads quickly in kindergarten and school. In a newborn, during the first 28 days of life, red eyes need urgent assessment. A child under 2 with a red eye should see a doctor. If a baby has watering and pus in only one eye, a blocked tear duct may be the cause. See a pediatrician or an eye doctor.
One red eye with pain
If one eye is red and it hurts, light bothers you or your vision drops, this is usually not simple conjunctivitis. Inflammation of the cornea or of the inner layers of the eye, and an acute glaucoma attack, which needs emergency care, can look like this. A red patch on the white of the eye without pain, after coughing or straining, is most often a small bleed and clears by itself. If it lasts more than a few days or keeps coming back, see a doctor.
Red eyes with measles and other infections
Red eyes with a fever, cough, runny nose and rash can be a sign of measles, especially in someone who is not vaccinated or has been near a sick person. Call the clinic before you go and tell them, so you do not infect others. For rashes, see Rash.
What you can do before the visit
- Wash your hands before and after touching your eyes, and do not rub them.
- Take out contact lenses and do not wear them until the exam.
- Use a separate towel and change pillowcases. You can wipe off discharge with a clean cloth dampened with warm water, a fresh one for each eye.
- Do not use someone else's drops, leftovers from earlier treatment or "redness relief" drops: they mask the picture and sometimes do harm. Leave the choice of drops to the doctor.
- Skip eye makeup while your eyes are red.
How an eye doctor finds the cause
The doctor asks when the redness began, whether one eye or both are affected, whether there is pain, itching or discharge, and whether you wear lenses. Then the doctor checks your visual acuity, examines the eye under a special microscope, uses a dye if the cornea may be damaged and, if needed, measures the pressure inside the eye or takes a swab. Treatment depends on the cause: some people need drops, others only hygiene and watching, and serious conditions are treated right away.