Red eye: What are the usual causes?

A red eye can be alarming but it is often an indication of a minor eye issue such as a rupture blood vessel or conjunctivitis. If pain is present, it might be a serious issue.

A doctor should be consulted if the individual has a red eye that does not seem to improve after a few days.

Consult a doctor or bring the individual to the nearest emergency department if the following are present:

  • Painful red eye
  • Other symptoms such as light sensitivity, visual changes, feeling sick or an intense headache
  • Recently had an eye injury especially if an object pierced it

What are the usual causes of a painless red eye?

The common causes of a painless red eye include minor issues such as conjunctivitis or a ruptured blood vessel. These conditions do not typically disrupt vision and eventually settle within 1-2 weeks.



The common causes of a painless red eye include minor issues such as conjunctivitis or a ruptured blood vessel.

The blood vessels on the eye are swollen which makes one or both eyes appear bloodshot or feel gritty. Other symptoms include watery eyes, itchiness and a sticky coating on the eyelashes.

Ruptured eye blood vessel

Coughing, straining or damaging the eye can oftentimes cause a blood vessel to rupture on the eye surface, resulting to a bright red blotch. This might appear alarming especially if the individual is using medications such as warfarin or aspirin since these lower the ability of the blood to clot which can worsen the redness. Luckily, this is not usually serious and settle on its own in a few weeks.

Causes of a painful red eye

If the red eye triggers discomfort or there are other symptoms such as visual changes, the cause is likely one of these conditions.

These conditions might be serious and even threaten vision, thus they require immediate assessment by a doctor.


This is characterized by inflammation of the iris or colored region of the eye. Aside from eye redness, it is also sensitive to light along with blurred vision and a headache.


This is an eye condition where the optic nerve which links the eye to the brain is damaged. Generally, the eye appears very red and painful along with seeing halos around lights. In addition, the vision might be cloudy or blurry.

Corneal ulcer

A corneal ulcer causes the eye to turn reddened and highly sensitive to light. There is also a sensation of something inside the eye.

Corneal abrasion or foreign object

A painful red eye is oftentimes caused by a foreign object such as grit or sand that enters the eye. If there is an object in the eye, a doctor should be consulted for proper removal.

More Information / Disclaimer

The information posted on this page on a red eye is for learning purposes only. Learn more about conditions and injuries that leads to a red eye by taking a standard first aid course with WinnipegFirst Aid.


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