How does oral rehydration therapy help recovering after gastroenteritis?

Replenish electrolyt. Gastroenteritis causes electrolytes especially sodium and potassium loss. Oral rehydration with tablets or powder replenishes these lost electrolytes in addition to water.

Related Questions

How effective is oral rehydration therapy for treating dysentery?

That depends on. Severity of case. In some situations oral rehydration works fine. In more severe cases- IV hydration may be required.