Why does our mouth water on seeing spicy food?

            Our mouth starts watering on seeing or smelling a spicy food because of the reflex action. The salivary glands in our mouth become active when we eat. The enzymes present in the saliva help in the digestion of food. But, sometimes, the glands start secreting large amounts of saliva even when there is no food in the mouth. This happens in anticipation of eating a tasty or spicy food when we see or smell it.

            On seeing or smelling a spicy food, nerve cells are stimulated and signals are sent to the brain which activate the salivary glands. The latter start secreting and our mouth start watering.