Preventing and treating dehydration from diarrhoea, vomiting, cholera, heat and high fever, in children and adults alike. They are the first treatment for childhood diarrhoea, usually alongside zinc.

The gut has a transporter that carries sodium and glucose across its lining together, and this transporter keeps working even when the gut is inflamed. Water follows the sodium across by osmosis. By supplying glucose and sodium in the right ratio, ORS opens a route for water to be absorbed that plain water, or a sugary drink, cannot use.

Mild nausea or vomiting if the solution is drunk too quickly. Giving small sips every few minutes, or by spoon for a small child, is better tolerated.

Make it up with the stated amount of clean or boiled and cooled water, never stronger or weaker, and never with milk, juice or a fizzy drink. Use the made-up solution within 24 hours, refrigerated. ORS treats dehydration, it does not stop the diarrhoea. Seek medical help for a child who is drowsy, has sunken eyes, passes no urine for many hours, vomits everything, or has blood in the stool.