Diarrhea is one of the most common medical complaints in the United States. It means frequently passing loose or watery stools. Diarrhea can be mild, with a few episodes during the day. You can also have severe diarrhea that strikes more than 10 times a day and accompanies other worrisome symptoms. In most cases, diarrhea is not harmful and resolves within a few days. But there are times when diarrhea is a concern. Acute Diarrhea Acute diarrhea is diarrhea that comes on suddenly and usually lasts 1 to 3 days, but can continue for as long as 2 weeks. The most common cause is a viral infection, or gastroenteritis. In children, rotavirus is the most common culprit. Norovirus is more common in adults. Bacterial and parasitic infections are also possible causes of acute diarrhea. With acute diarrhea, you may also have cramps, bloating, nausea, vomiting or fever. The biggest danger is dehydration due to loss of fluids in the stool. Signs and symptoms of dehydration include: Dark-colored urine Excessive thirst Fatigue, dizziness or lightheadedness Headache Skin that remains raised after pinching it, instead of flattening back out Urinating less than normal It can be hard to tell if infants, toddlers and children are becoming dehydrated when they can’t tell you how they feel. In infants and young children, signs of dehydration to look for include: Dry mouth and tongue Listlessness or irritability No tears with crying No wet diapers for 3 hours Sunken eyes, cheeks, or soft spots Treating acute diarrhea focuses on preventing dehydration. You need to drink plenty of liquids to replace fluids lost in the stool. You also need to replace electrolytes with choices like sports drinks or salty broths. For children, choose oral rehydration solutions, such as Pedialyte. You can also eat bland foods, such as rice or plain crackers or toast. Avoid foods that can worsen diarrhea, such as greasy, fatty, spicy, or high-fiber foods. Adults with viral diarrhea can use over-the-counter anti-diarrheal medicines. Avoid these medicines if you have bloody diarrhea or high fever, which can be signs of a bacterial or parasitic infection. They can worsen the diarrhea if this is the case. And do not use these medicines at all in children. Chronic Diarrhea Chronic diarrhea lasts for 4 weeks or longer. It typically signals something other than a viral infection as the root cause. It could be something simple, such as a food intolerance, or it could mean a more serious condition, such as colon cancer. In general, doctors classify chronic diarrhea as: Malabsorptive diarrhea—fatty diarrhea from impaired absorption of fats in the small intestine. There can be several reasons for this, including cystic fibrosis and other problems with pancreatic enzymes, which help us digest food. Inflammatory diarrhea—the most common cause is inflammatory bowel disease (either Crohn’s disease or ulcerative colitis). Watery—there are several potential causes of watery diarrhea including food intolerances and medication side effects. Other causes of chronic diarrhea do not fit neatly into one of the three categories. International travelers may have acquired an intestinal parasite. Irritable bowel syndrome and uncontrolled diabetes are other good examples. Finding the cause of chronic diarrhea usually involves testing. This could include lab tests, stool samples, and imaging tests to look at the bowel and how it functions. Treating chronic diarrhea depends on the underlying cause. When to See a Doctor Diarrhea is usually not an urgent medical problem. However, dehydration can be life threatening. Dehydration is especially dangerous in infants, young children, older adults, and people with a weakened immune system. Seek immediate medical attention for signs and symptoms of dehydration. You should also find medical care right away for severe diarrhea or any of the following symptoms: Black, tarry stools Blood or pus in the stool Diarrhea that does not improve after 24 hours in a child. Although the underlying problem may not serious, a doctor should examine the child and may order testing to rule out serious causes and determine if additional treatment is necessary. A doctor can also recommend diarrhea treatment appropriate for the child’s weight. Fever higher than 102 degrees Fahrenheit Severe abdominal or rectal pain In addition, adults should not wait until they have had diarrhea for a week. See your doctor if diarrhea does not improve within 2 to 3 days.