Diarrhea can strike anyone at any time and can last from a few uncomfortable days to many agonizing months. Many different factors may trigger diarrhea, including infections, food intolerances, intestinal disorders, and medications. According to the National Institutes of Health, the average adult can expect about four bouts of acute diarrhea per year. Children in the United States average seven to 15 episodes of diarrhea by age 5.

Acute diarrhea, which lasts for a few days, is typically due to a viral or bacterial infection. In contrast, chronic diarrhea, which persists for two weeks or longer, is more likely to be caused by underlying digestive conditions, like irritable bowel syndrome (IBS) or an inflammatory bowel disease (IBD), such as Crohn's disease or ulcerative colitis.

Causes of Diarrhea: Gastrointestinal Infections

Gastroenteritis, or inflammation and irritation of the digestive tract that leads to vomiting and diarrhea, is usually caused by an infection. Common gastrointestinal infections often blamed for diarrhea include:

  • Bacteria such as salmonella, shigella, and E. coli, which are spread by ingesting contaminated food or water
  • Viruses like rotavirus, cytomegalovirus, and viral hepatitis
  • Parasites like cryptosporidium, Giardia lamblia, and Entamoeba histolytica, which can be contracted by ingesting contaminated food or water

Diarrhea due to infection can happen at any time, but eating undercooked meats or unrefrigerated food, traveling to other countries, drinking from or swimming in bodies of fresh water, and coming into close contact with someone who has gastroenteritis are all risk factors.

Causes of Diarrhea: Other Triggers

Many different factors can affect digestive health and irritate the digestive tract. Besides infection, other diarrhea triggers may include:

  • Sensitivity to certain foods such as dairy products (lactose intolerance) and artificial sweeteners
  • Intestinal disorders like Crohn's disease, ulcerative colitis, celiac disease, and IBS
  • Gallbladder or stomach surgery
  • Hereditary disorders like cystic fibrosis and enzyme deficiencies
  • Disorders of the pancreas or thyroid
  • Cancer-fighting radiation therapy to the abdomen or pelvis

Additionally, a number of medications can cause diarrhea as a side effect. If you've started taking a new drug and notice frequent, loose stools, ask your doctor if the medication could be to blame. Some specific types of drugs that commonly lead to diarrhea are antibiotics, antacids, cancer treatments (including chemotherapy), high blood pressure medications, and some laxatives.

No matter what's causing your diarrhea, be certain to avoid heavy foods like greasy, fatty, or sugary fare until your belly gets better. Also, make sure to drink plenty of fluids and stay away from alcohol and caffeinated drinks, which can be dehydrating.

Staying hydrated is critical when dealing with diarrhea, since your body can lose large amounts of water through the digestive tract. If your diarrhea is persistent or you notice signs of dehydration like dry mouth or skin, changes in the color or the amount of urine, and fatigue, contact your doctor. Also, call your doctor if your stool is black or bloody or you have a fever. Your doctor can test your blood and stool to determine the cause of your diarrhea and begin proper treatment.