Hypotonic hydration is a term that describes a condition that occurs when a person consume large amounts of water. Hypotonic refers to the concentration of salts is lower (hypo) than saline (isotonic). Hypotonic hydration may occur with extremely high water intake or kidney damage. When the concentration of the various substances (salts, proteins, etc.) decreases in plasma (and the body in general) the consequence is that the extracellular space increases in volume and salt concentrations in the body decreases. When the salt concentration decreases in the extracellular space, it means that the fluid will enter the cells where there is a higher concentration of salts, and the cells swell. This is especially harmful to nerve cells.