You have been told many benefits of drinking milk since childhood. Milk is very important for health. You must have heard many times the elders say that one should never drink water after drinking milk. Or, one should never eat citrus fruits after drinking milk. This is the main reason.
Never drink water immediately after drinking milk. This causes stomach upset. Also, if the water is drunk immediately after drinking milk, then the body does not get the nutritional properties of milk.
If water is drunk immediately after drinking milk, then the metabolism of the body becomes slow. That is, if you drink water, you will not digest milk. This will make you feel acidity.
Never drink milk immediately after eating food. This can cause problems such as food poisoning, gas, indigestion, vomiting, abdominal pain, loose motion. The reason behind this is the mixing of salt and oil in food. Both of these are conflicting with milk.