The Red Eye

Red eye


There are lots of reasons an eye can be red.

Some common ones include:

  • infection
  • inflammation
  • trauma
  • foreign body

Getting hit in the eye or getting dirt or soap in the eye are usually pretty obvious and require evaluation and treatments that we’ll put aside for now.

Infection and inflammation can be picked apart, but sometimes it’s complicated and they overlap: what starts out as allergy and inflammation can be touched and rubbed. This can lead to infection.

First, some basics. The red eye, commonly called “pink eye” is more correctly called conjunctivitis. The conjunctiva is the layer that wraps the eye–think of plastic wrap–and whenever you see –itis after a body part that means inflammation. So conjunctivitis is inflammation of the conjunctiva.

What inflames the conjunctiva? Usually allergy or infection.

With allergy (allergic conjunctivitis), the eye is swollen, itchy and red. There can also be a watery discharge. This is treated with cool compresses and antihistamines (loratadine, cetirizine, fexophenadine, diphenhydramine) taken by mouth as well as applied as separate antihistamine eye drops.

With infection, the eye is swollen and there’s usually a discharge.

Eye infections can be caused by viruses or bacteria. They can be spread by getting coughed or sneezed on and by touching something infected with viruses or bacteria–think towels, surfaces, your hands–and then touching the eye.

Call the doctor for the red eye because it’s often difficult to differentiate viral conjunctivitis from bacterial conjunctivitis. Both require specific treatments. Bacterial conjunctivitis, because it’s caused by bacteria, is treated with antibiotic eye drops your doctor will prescribe. Very young children with infectious conjunctivitis will also often have an ear infection.

Infectious conjunctivitis is highly contagious. Children are usually excluded from daycare or school for 24 hours while treatment (usually eye drops) are begun. Wash and change the sheets and towels to keep it from spreading in the hospital and keep surfaces clean.

One good way to avoid conjunctivitis–and infections in general–is to never touch your eyes, nose or mouth unless you’ve just washed your hands. This is impossible for young children, but worth teaching your school age child and practicing yourself.

About Lisa M. Asta, MD

Lisa M. Asta, M.D. is board-certified by the American Board of Pediatrics and is a Fellow of the American Academy of Pediatrics, for which she is also a Media Representative (she has been interviewed for “Kids Health” on Health Radio, and quoted in Parenting Magazine, USA Today, and the New York Times, among other publications). She is a Clinical Professor of Pediatrics at the University of California at San Francisco and past pediatric chair at John Muir Medical Center in Walnut Creek. She graduated from Temple University School of Medicine and the Johns Hopkins University. Dr. Asta is also a writer whose fiction has appeared in Inkwell, Philadelphia Stories, Schuylkill, and Zeniada. Her essays have appeared in the Journal of the American Medical Association, Hippocrates, the San Jose Mercury News, and The New Physician Magazine. She is an occasional contributor to KQED public radio’s Perspectives series, and has written articles for Bay Area Parent, Valley Parent, Parents’ Press, and Parents Express, as well as online at,, and She wrote a chapter in The Field Guide to the Normal Newborn, ed. Gary Emmet, M.D. currently has two how-to videos for parents in production which feature Dr. Asta. For more on Dr. Asta’s writing, visit
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