The common belief is that drying of mouth or throat is the out come of thirst only. But, this is not true. Such drying can take place because of many other reasons. When do we play outside for longer period, our throat becomes dry, when  do we exercise, our throat also becomes dry. Again when we become tensed, we feel thirsty. So the question arises, ‘why do we feel thirsty’?

  It is well known to all of us that water and salt are always take place in our blood. The body tissues also contain these substances. In normal conditions, the proportion  of these two materials in blood remains same. So, if because of any reason the level of water in blood gets reduced, the proportion of the two materials also varies. In such a situation the thirst centre situated in the brain sends messages to the throat. As a result of this the throat begins  contracting. This contraction makes the throat dry, we feel thirsty and so we drink water.

                However, sometimes the salivary glands produce sufficient saliva and our stomach and blood too have sufficient water and yet we feel thirsty. For example when we eat too much salted snacks, we feel thirsty. So, the consumption of salted food make us feel thirsty. Consumption of salted food increases the amount of salt in blood. The quantity of salt in blood exceeds the normal level and this alters the normal proportion of salt and  water in blood. As a result of this we feel thirsty.

    Hence, we feel thirsty not because of the drying of  our mouth or throat but due to the varying in the proportion of water and salt in our blood.