Question

A person takes concentrated solution of salt after sometime he starts vomiting why

Answer 1

The use of a salt solution containing excess of salt to cause vomiting has been in practice since a very long time. Salt has a water retention property. When a solution containing excess of salt is taken, then due to osmosis water will move into the intestine, putting pressure on the intestinal walls. This also causes nausea. The intestinal wall is not able to tolerate this strain, and hence this excess water retention causes vomiting. 

Thus we can say that the phenomena responsible for vomiting after taking a concentrated salt solution is osmosis. 

Answer 2

When a solution containing excess of salt is taken, then due to osmosis & due to phagocytocic nature of cells he vomitied