For diarrhea, start by drinking oral rehydration solution; do not give anti-diarrheal drugs to children under 5

The most important thing during diarrhea is rehydration, not stopping the diarrhea itself. Mix the solution exactly as directed on the package and drink it — never substitute it with sugary juices or soft drinks, as the excess sugar can actually worsen dehydration. Never give anti-diarrheal medications such as loperamide to kids under 5 years old; in severe cases these drugs can cause life-threatening intestinal blockages.

A box of oral rehydration solution costs just a few dollars, so it’s worth keeping one at home.

WHO’s guidelines on diarrhea treatment state clearly that anti-diarrheal and anti-vomiting drugs provide no real benefit for children with acute or prolonged diarrhea. They do not prevent dehydration or improve nutritional status, and some carry serious, even fatal side effects — so they must never be given to children under 5. Drugs like loperamide that slow intestinal motility can lead to severe paralytic intestinal obstruction, which is potentially fatal and can prolong the underlying infection. The same guidelines also warn that drinks high in sugar draw water into the intestines, causing hypernatremic dehydration; this applies to soft drinks and most commercially sold fruit juices. WHO recommends a low-osmolarity formula with a total osmotic pressure of 245 mOsm/L; compared to older formulations, this reduces unplanned intravenous fluid administration by 33%. A Cochrane review of 8 trials reached similar conclusions (OR 0.59, 95% CI 0.45–0.79), showing roughly a 40% reduction in complications when this solution is used.

When purchasing oral rehydration solution, always check the package label for its osmotic pressure and choose the low-osmolarity version. The WHO guidelines also note that blood in a child’s stool almost always indicates bacterial dysentery, which requires medical treatment with antibiotics — rehydration alone is not sufficient. The “moderate” benefit rating here reflects the fact that the available data compares two different rehydration solutions rather than the effect of drinking any solution versus none.

World Health Organization (2005). The treatment of diarrhoea: a manual for physicians and other senior health workers, 4th revision. https://iris.who.int/handle/10665/43209（中文版《腹泻治疗：医生和高年资卫生工作者使用手册》第 2.6 节，同一页面下载）；Hahn S, Kim S, Garner P (2002). Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children. Cochrane Database of Systematic Reviews, (1):CD002847. https://doi.org/10.1002/14651858.CD002847