How does dehydration set in during diarrhoea?

The diarrhoea spreads through infection by contaminated food, water, drinks, hands, clothes etc. During diarrhoea frequent loose motions and vomiting leads to dehydration.
To control the dehydrationo during diarrhoea; Saline drip may be given intravenously to maintain fluid and electrolytes in the body. Alternatively oral rehydration solution (ORS) may be given to the patient periodically.