In adults diarrhoea is usually caused by a virus infection and is therefore unable to be treated directly. The symptoms can usually be eased by the traditional kaolin and morphine mixture or by medicines containing codeine.
Holiday diarrhoea is often due to bacteria. Again, kaolin and morphine can be taken.

In both the above cases, consult your doctor if the symptoms persist for more than a few days.

Diarrhoea in very young children and babies needs careful attention.  Most babies have loose bowel action during their first six months due to their predominantly liquid diet.  Sudden bouts of unusually watery diarrhoea should be treated by taking the baby off solids and feeding it a cooled solution of boiled water with a teaspoon of sugar and a pinch of salt to the pint.  If the symptoms persist for more than 24 hours, or are accompanied by vomiting or weakness, consult your doctor.