The rehydration unit in an Indian slum
24 July 2014 Last updated at 11:57 BST
Oral rehydration salts (ORS - also known as Oral Rehydration Therapy) is just a mixture of sugar, salt and water in the right proportions. It's simple, doesn't need to be administered by a doctor and is effective in treating diarrhoea.
Although these effects are well known, many people around the world do not have access to this vital treatment.
Rahul Tandon reports from Calcutta where a charity has incorporated a rehydration unit into their health centre, ensuring the local community can get ORS and learn more about the treatment.
More stories from Health Check