Acute diarrhea (lasting less than 2 weeks)

Antibiotic use

Recent use of antibiotics

Often no other symptoms

A doctor’s examination

Sometimes tests for Clostridioides difficile toxin in stool

Gastroenteritis due to viruses, bacteria, or parasites†

Often with vomiting

Dehydration common especially among infants and young children

Sometimes fever and abdominal pain

Rarely blood in stool

Sometimes recent contact with infected people (such as those at a day care center, at a camp, or on a cruise), with animals at a petting zoo (where Escherichia [E.] coli may be acquired), or with reptiles (which may be infected with Salmonella bacteria) or recent consumption of undercooked, contaminated food or contaminated water

A doctor’s examination

Sometimes examination and testing of stool

Food allergy

Hives, swelling of the lips, and difficulty breathing within minutes to several hours after eating

Sometimes vomiting

Often an already identified food allergy

A doctor’s examination

Hemolytic-uremic syndrome

Abdominal pain, vomiting, and usually bloody diarrhea for a few days, followed by development of pale skin and decreased urination

Sometimes bleeding in the skin (seen as tiny reddish purple dots or splotches)

Blood tests

Examination and testing of stool

Chronic diarrhea (lasting 2 weeks or more)

Allergy to cow's milk protein

Vomiting

Poor feeding

Weight loss, poor growth, or both

Blood in stools

Stool tests

Symptoms that lessen when the formula is changed

Possibly endoscopy, colonoscopy, or both

Excessive consumption of fruit juices (especially apple, pear, and prune)

Drinking more than 4–6 ounces (120–180 milliliters) of fruit juice a day

Often no other symptoms except diarrhea

A doctor’s examination

Resolution of diarrhea after decreasing consumption of fruit juices

Inflammatory bowel disease such as

• Crohn disease

• Ulcerative colitis

Blood in stool, crampy abdominal pain, weight loss, loss of appetite, and poor growth

Sometimes arthritis, rashes, sores in the mouth, and tears in the rectum

Colonoscopy

Sometimes CT or x-rays after barium is inserted in the rectum (barium enema)

Lactose intolerance (inability to digest lactose, the sugar in milk and dairy products)

Abdominal bloating, passing of gas (flatulence), and explosive diarrhea

Diarrhea after consumption of milk and dairy products

A doctor’s examination

Sometimes a breath test to detect hydrogen (indicates undigested carbohydrates)

Examination and analysis of stool to check for unabsorbed carbohydrates

Malabsorption disorders such as

• Celiac disease

• Cystic fibrosis

• Acrodermatitis enteropathica

Light-colored, soft, bulky, and unusually foul-smelling stool that may appear oily

Abdominal bloating and flatulence

Poor weight gain

With cystic fibrosis, frequent respiratory infections

With acrodermatitis enteropathica, rash and cracks in the corners of the mouth

Examination and testing of stool

If celiac disease is suspected, blood tests to measure antibodies against gluten (a protein in wheat) and biopsy of the small intestine

If cystic fibrosis is suspected, a sweat test and possibly genetic testing

If acrodermatitis enteropathica is suspected, a blood test for zinc deficiency

A weakened immune system due to

• HIV infection or an immunodeficiency disorder

• Use of drugs that suppress the immune system

Frequent infections

Weight loss or poor weight gain

Sometimes an already identified HIV infection

Blood tests for HIV

A complete blood cell count and other blood tests to evaluate the immune system