does it necessarily mean that hypertonic and hypotonic solutions are dangerous when attained by a cell?

Answer 1

An hypotonic solution is dangerous, since the water enters the cells when the cells are in an hypotonic medium. Example : an isotonic solution is NaCl 9g/l. When you put red cells in a medium of less than 3g/l of NaCl, the red cells breaks.

Hypeetonic are also dangerous since the water goes out the cells

Answer 2

An example from my perspective, medically; A person who is diabetic, the pancreas is not working properly for whatever reason. The symptom of thirst is caused by the action you have described. When the person consumes a sugar-loaded diet, the intracelluar fluid is drawn out of the cell by the now hyperosmolar interstitial fluid, thereby causing the pt. to feel thirst. He replaces the lost fluid to the cell by drinking water until the cells are hydrated and he feels satiated. In the meantime, the body tissues can become saturated by the excess fluid which the unhealthy body is unable to rid itself of, thereby presenting as edema in tissue until the kidneys go into overdrive and diuresing occurs. The same thing happens with the body's consumption of salt in a person who does not have the capacity to handle the excess as in kidney disease, hypertension, etc.
You can also reverse this to make the cell hypertonic but it still would present an insult to the body as a whole.