In adults, diarrhoea is usually caused by a viral infection and is therefore unable to be treated directly. The symptoms can usually be setted by simple over the counter medications. Holiday diarrhoea is often due to bacteria.
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 them a cooled solution of boiled water with a teaspoon of sugar and a half a teaspoon of salt to the pint or purchase oral rehydration salts from the pharmacy.
If the symptoms persist for more than 24 hours, or are accompanied by vomiting or weakness, consult your doctor.