We’ve all felt the awful abdominal pain that comes with diarrhea — that “I’m afraid I won’t make it” sort of pain; the “dear God, what have I done wrong?” kind of pain. Usually diarrhea just works itself out of your system, in every sense of the phrase. But in rare cases, it can be a symptom of a serious problem in your body.

Parasite

If you drink food or water contaminated with the parasite Giardia, the resulting diarrhea can be pretty severe. “Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection,” the Centers for Disease Control and Prevention say, and the symptoms — which may also include gas, cramps, nausea, dehydration and greasy stools that tend to float — can last longer than two weeks. There may also be itchy skin and swelling in the eyes or joints. Children have it the worst: “severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition.”

Crohn’s disease

The Crohn’s and Colitis Foundation of America estimates this chronic condition of inflammation in the gastrointestinal tract, one of a group referred to as inflammatory bowel diseases, affects about a quarter of 1 percent of the U.S. population. It usually affects the area where the small and large intestines meet and comes with persistent diarrhea, rectal bleeding, the urgency to poop, cramps and pain, constipation and an incomplete feeling after pooping. The foundation notes that some may lose their appetite, and thus lose weight, and feel fatigued. “In more severe cases, Crohn’s can lead to tears (fissures) in the lining of the anus, which may cause pain and bleeding, especially during bowel movements” or other abnormalities.

Hepatitis

Some viruses can cause inflammation in the liver, which filters the blood, helps to digest food and fights infection. Hepatitis A, B or C are all viruses that impair the liver, in order of prevalence, creating a condition known as viral hepatitis. The Centers for Disease Control and Prevention, in comparing the three, note that while many people do not show symptoms — and thus do not know they are infected — hepatitis may also present with fatigue, appetite loss, fever, nausea, abdominal pain, dark urine, gray stool, joint pain and jaundice, which is a yellowing of the skin and the whites of the eyes.

Artificial sweeteners

This is more of a problem linked to lifestyle. People who think they are being healthy by cutting out real sugar might get more than they bargained for if they are sensitive to artificial sweeteners like sorbitol, which are found in chewing gum, sports drinks and other sugar-free products. Men’s Health notes that the artificial sweeteners draw water from the intestines, so they can cause diarrhea.