Common Causes of Red Eyes

Posted on February 4, 2018

“Red eye” is a situation we are all familiar with, we’ve all experienced it sometime or the other. Red eyes range from irritated and bloodshot eyes to an asymptomatic pinkish hue, to a few dilated and prominent blood vessels which look like contorted red lines across the white of the eye. The redness is usually due to the blood vessels in the outermost covering of the eye, this include the conjunctiva, episclera (loose tissue above the sclera) and sclera (white portion of the eye).

Red eyes may be caused by eye allergies, dry eyes, fatigue, over use of contact lenses or common eye infections such as pink eye (conjunctivitis). Red eyes may also associated with serious eye diseases like glaucoma and uveitis, and therefore must not always be dismissed as trivial. In fact, should the red eyes not resolve, or worsen, or be associated with pain, you must always contact your eye doctor for an opinion.

Causes and Precautions


Conjunctivitis is one of the most common causes of a red eye. It can be allergic or infectious. The former is characterized by a ropy discharge, and is not contagious. The latter is accompanied by a dirty discharge and matting of eyelids, and is often caused by a virus.

When your immune system reacts to a foreign substance, such as pollen, dust or certain chemicals found in makeup, an allergic reaction happens. This causes histamine release, which causes the blood vessels to dilate, leading to watery, red eyes.

An infective conjunctivitis occurs when the conjunctiva, the outermost milky membrane covering the eye, gets infected, either by a virus. The infection, like the allergy, evokes the body’s defense mechanism to fight off the infection, and causes the blood vessels to swell and become prominent, resulting in the red eye.

Your doctor is the best judge of whether the conjunctivitis has been caused by an allergy, or by infection, and if the infection is bacterial or viral, and will treat them accordingly.

Dry Eyes

When the tear film that keeps your eyes lubricated is either deficient, the eyes become red, sore and irritated. This condition is called dry eyes and can be due to two reason. Either the tears are deficient in quantity, or quality. This improper lubrication results in a chronic inflammation of the surface of the eye, and can vary in degree from mild to very severe.

Over use of screen devices, computers and mobile phones may aggravate dryness due to computer vision syndrome. In this case, it is important to decrease the screen time, and to remember to blink frequently, and to take frequent breaks.

Dry eyes, in the early stages, can easily be managed by over the counter lubricating drops, but moderate to severe disease needs an ophthalmologist’s attention. Your eye doctor may also consider using gels and ointments, as well as punctual plugs if required. He or she may also treat the underlying cause predisposing your eyes to dryness.

Contact Lenses

Contact lens users are at special risk of developing dry eyes. This may be due to several reasons ranging from dryness, allergic reaction to contact lens solution, improper cleaning of lenses to severe, and vision threatening complications like corneal ulcer.

Therefore, if you wear contact lenses and develop red eyes, you must remove your contact lenses immediately, and contact your doctor.

It is also imperative to maintain proper hygiene with contact lenses: your hands must be cleaned when handling lenses, you must disinfect your contact lenses carefully, and you must not wear them for longer hours than recommended. Since contact lenses also can worsen dry eye syndrome, your doctor may recommend preservative free lubricating eyes drops to keep you comfortable.


Subconjunctival hemorrhage or bleed just beneath the conjunctiva can be caused due to trauma or injury to the eye, bout of violent cough, or an episode of elevated blood pressure.

Eye injuries can range from minor scratches or abrasions on the cornea, to chemical injuries, lacerations and rupture of the eyeball. These terms are self-explanatory, and obviously need urgent medical attention from a tertiary care eye hospital.

Corneal Ulcer

Corneal ulcer, keratitis or infection of the cornea can be caused by viruses, bacteria or fungus. These infections may be potentially sight-threatening and are considered to be an ocular emergency. Corneal ulcers are invariably painful, and may be accompanied by decrease in vision and discharge.


Uveitis is an inflammation of the middle coat of the eye, called the uvea. It can affect just the iris (iritis) or penetrate deep into the eye (posterior uveitis). This is also a potentially sight threatening condition, and may be accompanied by light sensitivity, pain and floaters, in addition to the red eye.


Glaucoma is a group of varied eye diseases in which the eye pressures become high and affect the optic nerve and the field of vision. Usually glaucoma is completely asymptomatic, but a particular variant called acute angle closure glaucoma causes an acutely painful red eye, along with a diminution of vision. This condition constitutes an ophthalmic emergency and must be attended to immediately.

Glaucoma patients on eye drops often develop red eyes due to the dry eyes caused by the medication. Some also develop allergies to their eye drops, while redness is a known side effect of many glaucoma medicines.


  • Don’t rub your eyes. Rubbing eyes transfers dirt, allergy causing agents and infectious bacteria from your hands to the eye and cause infections and aggravate allergies. In addition, vigorous rubbing can cause corneal abrasions, subconjunctival hemorrhages and can worsen trauma.
  • Take proper care of your contact lenses. Use daily disposable lenses whenever possible, be careful with make-up, and make sure your hands have been cleaned meticulously when handling your lenses. Also, do not wear them for longer than prescribed, and do not sleep with your contact lenses in the eye. Also, follow your doctor’s instructions about cleaning and replacing your contacts without fail.
  • Remember the 20-20-20 rule. Look away from your computer screen every twenty minutes, close your eyes for 20 seconds and look at an object at least 20 feet away to relax your eyes for 20 seconds.
  • Do not self-medicate beyond lubricating eye drops. Be very wary of steroid drops and eye-whitening ayurvedic or “natural” eye drops. Do not use rose water, kajal or surma in the eye as a remedy for red eyes, they will only aggravate the situation. Only your eye doctor can prescribe steroid drops in the proper dosage, for the proper indications.
  • Remember all medications must be prescribed by your eye doctor after a proper eye examination, so make sure you reach out to your doctor for help in case of a red eye that persists or worsens, or is accompanied by any other symptoms.

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