If red blood cells are placed in a hypertonic solution, more water leaves than enters, and this will cause cells to shrink.
The swelling or shrinking of cells can damage them. Human cells are about .9% saline (or salt water), so if cells are placed in a solution that is higher than .9% saline, water will diffuse from the cells causing them to shrink. This hypertonic solution is caused by the need for the solutions to always be at equilibrium.
Just recently, two scientific papers that initially electrified biologists by describing an easy way to make stem cells were retracted by the journal that published them after they were found to be riddled with “critical errors.” Find out more at The New York Times.