What causes bloodshot eyes?

Although bloodshot eyes can be caused by relatively mild conditions, such as dry eyes or the common cold, bloodshot eyes can also be caused by serious or life-threatening conditions, such as an anaphylactic reaction or acute glaucoma, both of which should be immediately evaluated in an emergency setting.

Infectious causes of bloodshot eyes

Bloodshot eyes can be caused by a variety of infections including:

  • Bacterial or viral conjunctivitis (inflammation of the eye surface)

  • Blepharitis (infected eyelash follicle)

  • Chalazion (inflammation of a blocked oil gland in the eyelid margin)

  • Common cold (viral respiratory infection)

  • Dacryocystitis (infected tear duct)

  • Iritis (inflammation of the iris)

  • Keratitis (inflammation of the cornea)

  • Orbital cellulitis (acute infection of the area surrounding the eye)

  • Scleritis (inflammation of the white of the eye)

  • Sinus infection or sinusitis

  • Stye (also called a hordeolum, which is an infected oil gland)

  • Uveitis (inflammation of the iris, choroid, and ciliary body in the eye)

Allergic causes of bloodshot eyes

Bloodshot eyes can be caused by mild to serious allergic reactions including:

  • Anaphylactic allergic reaction to any substance

  • Drug allergy, such as penicillin or codeine

  • Hay fever or allergic reaction from animal dander, dust, cosmetics, or pollen

  • Insect bite allergy such as bee sting

Traumatic and other physical causes of bloodshot eyes

Bloodshot eyes can arise from injury and other physical conditions including:

  • Contact lens use

  • Coughing or straining

  • Eye injury or surgery

  • Facial burn or other trauma

  • Foreign object in eye

  • Hyphema (bleeding inside the front of the eye behind the cornea)

  • Scratches on the cornea

  • Subconjunctival hemorrhage (broken blood vessel on the white of the eye)

Other causes of bloodshot eyes

Bloodshot eyes can be due to various other diseases, disorders and conditions including:

  • Acute glaucoma

  • Blocked tear duct

  • Corneal ulcer

  • Dehydration

  • Dry eyes

  • Ectropion (turned-out eyelid)

  • Entropion (turned-in eyelid)

  • Eye fatigue

  • Keratoconus (cone-like cornea)

  • Pinguecula (yellowish, benign growth on the conjunctiva near the cornea)

  • Pterygium (fleshy, benign growth on the sclera that may extend onto the cornea)

Questions for diagnosing the cause of bloodshot eyes

To diagnose the underlying cause of bloodshot eyes, your doctor or licensed health care practitioner will ask you several questions related to your symptoms. You can best help your health care practitioner in diagnosing the underlying cause of bloodshot eyes by providing complete answers to these questions:

  • When did your symptoms start? Does the redness come and go or is it constant?

  • Have you had any change in your vision or visual disturbances?

  • Did you eat any foods or come in contact with any unusual substances preceding the onset of your symptoms?

  • Do you have any pain, shortness of breath, or other symptoms?

  • Provide your full medical history, including all medical conditions, surgeries and treatments, and family history. What medications and dietary supplements do you take?

What are the potential complications of bloodshot eyes?

Complications associated with the underlying causes of bloodshot eyes can be progressive. Because bloodshot eyes can be due to serious diseases, failure to seek treatment can result in complications and permanent damage. It is important to contact your health care provider when you have bloodshot eyes or other unusual symptoms that persist or become worse with time. Once the underlying cause is diagnosed, following the treatment plan outlined by your doctor can help reduce potential complications including:

  • Loss of the eye and orbital contents.

  • Loss of sight (blindness)

  • Spread of infection to other parts of the body including the blood


  1. Diseases & Conditions. American Academy of Ophthalmology. http://www.geteyesmart.org/eyesmart/diseases/index.cfm.
  2. Eye Problems. FamilyDoctor.org. http://familydoctor.org/online/famdocen/home/tools/symptom/505.html.
  3. Eye Redness. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003031.htm.
  4. What Is a Pinguecula and a Pterygium? American Academy of Ophthalmology. http://www.geteyesmart.org/eyesmart/diseases/pinguecula-pterygium.cfm.

What are bloodshot eyes?

Bloodshot eyes describe a condition in which the whites of the eyes appear red. Bloodshot eyes occur when the blood vessels in the sclera (the white of the eye) dilate or swell. A variety of mild to serious diseases, disorders and conditions can irritate the blood vessels of the sclera and cause bloodshot eyes.

Bloodshot eyes are often due to mild conditions, such as eye Read more about bloodshot eyesintroduction


What other symptoms might occur with bloodshot eyes?

Bloodshot eyes may occur with other symptoms, which vary depending on the underlying disease, disorder or condition. For example, bloodshot eyes due to dry eyes may be accompanied by irritation or eye pain. Bloodshot eyes caused by infection may include eye discharge, swelling, pain, and red eyelids. If you have other symptoms along with your eye symptoms, be sure to tell your health care provi... Read more about bloodshot eyessymptoms

Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Eyes and Vision

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