Health A-Z

Medical Content Created by the Faculty of the Harvard Medical School


What Is It?

Diarrhea is more frequent and more liquid bowel movements than normal. There are many causes. Diarrhea often is caused by an infection with bacteria, viruses or a parasite. Bacteria cause diarrhea either by invading the intestine or by producing a toxin that makes the intestine secrete more water. When the diarrhea is caused by food contaminated with bacteria or parasites, people often refer to this as food poisoning.

Other causes of diarrhea include:

  • Irritable bowel syndrome, especially during times of increased stress

  • Side effects from medications, such as antibiotics and magnesium-containing antacids

  • Overuse of laxatives

  • Inflammation of the lowest part of the intestine (ulcerative colitis or Crohn's disease).

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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