This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
Charcoal acts well in the diarrhoea of scrofulous children when the stools are small, slimy, and light-colored, with intermediate troublesome discharge of flatus and itching of the anus; also when the attacks have depended upon irritation of the mucous membrane from undigested food, etc. It may be well given with milk (cf. Medical Record, March, 1881). Rhubarb is often usefully combined with it in the cases described.
Charcoal is also serviceable in the atonic irritative diarrhoea of old people, but I have more than once known intestinal hemorrhage occur after its use. If large quantities be given, some may be retained and act as a mechanical irritant, so that the remedy is not so innocent as commonly thought.