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Conjunctivitis is an inflammation of the mucous membrane (covering) of the eye or eyelid. Infectious conjunctivitis, or "pink eye," is a highly contagious infection that is usually caused by a virus or bacteria. It is more common among children than adults. When conjunctivitis is triggered by allergies, it is called allergic conjunctivitis and can affect anyone with allergies.

What is the difference between infectious conjunctivitis and allergic conjunctivitis?

Infectious conjunctivitis is caused by bacteria or a virus and spreads very easily from one person to another. If someone touches or wipes an infected child's face and then touches his or her own eyes, the infection may be transferred. In addition, the infection can be spread through objects such as towels, tissues, or an infected contact lens.

Allergic conjunctivitis is the eye's reaction to an allergen. Exposure to the allergen triggers the watering and itching of the eyes. Unlike infectious conjunctivitis, allergic conjunctivitis is not contagious. Although any allergy can trigger conjunctivitis, it is caused most frequently by cats or seasonal allergies, such as tree pollen in the spring.

Infectious conjunctivitis usually starts in one eye and can spread to the other. Allergic conjunctivitis typically affects both eyes.

What are the symptoms of conjunctivitis?

  • Itchy eyes is the main symptom for allergic conjunctivitis.
  • Usually both eyes are affected with allergic conjunctivitis.
  • Burning, scratchy, or sandy eyes suggest an infection.
  • Bloodshot, watery eyes can occur with both allergic and infectious conjunctivitis.
  • Crusting of the eyelashes suggests an infectious cause.

How is conjunctivitis treated?

Treatment of conjunctivitis depends on its cause:

  • Viral conjunctivitis cannot be treated with antibiotics, but it generally just goes away with time.
  • For bacterial conjunctivitis, use antibiotic drops or ointment on the affected eye.
  • For allergic conjunctivitis, the easiest way to manage the reaction is to avoid the allergen (the object that is causing the allergic reaction). A cool compress on the eyes may relieve some of the symptoms and help prevent rubbing the eyes. In other circumstances, topical, anti-inflammatory eyes drops or a topical antihistamine will relieve the itching.

How can you prevent conjunctivitis?

Viral and bacterial conjunctivitis are highly contagious. In daycare centers, the infections can spread quickly from child to child. To prevent the transmission of infection, caregivers and children should wash their hands frequently, especially if one child develops the infection. Children should not share towels or any other object that touches the face (such as pillows and stuffed animals). Children with conjunctivitis should not attend school or daycare until the infection has cleared up completely.

People who suffer from allergic conjunctivitis should try to minimize their exposure to the allergen if possible. Wear glasses outdoors, and avoid touching your eyes. Your doctor may recommend allergy medications that will reduce your chances of developing the inflammation.


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Review Date: 6/29/2011
Reviewed By: Paula J. Busse, MD, Assistant Professor of Medicine, Division of Clinical Immunology, Mount Sinai School of Medicine, New York, NY, Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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