There is a tendency in current medical research to explore the importance and symptomatology of saliva. The question to which increasingly more researchers from the medico-legal, systemic and dental fields tried to answer and bring together arguments for a greater emphasis is referring to the role of saliva in the health of the patient. Up until our time, people have looked at the importance of saliva from another perspective: saliva helped in pasting envelopes or stamps, or mostly in reported cases of public speakers faced with the impossibility of having a coherent speech due to sensations of dry mouth. This 'dry mouth' condition, named xerostomia in medical terms, has been used since antiquity as a test in detecting lies, knowing since then that the inhibition of emotional salivary glands, the feeling of 'dry mouth' is caused by anxiety, thus being a potential incrimination. Although hundreds of publications have insisted on the etiology and complications of the salivary gland hypofunction, only a few health professionals used to harvest saliva tests. As in the case of urine and blood, saliva quality and quantity are affected by a multitude of medical conditions and treatments, as well as the patient's psychological state. A review of the formation, function and dysfunction of salivary glands may convey the significant role played by saliva in health and disease, especially in detection and recognition of salivary gland hypofunction, systemic disease, and the psychological states, and thus prevent complications caused by these conditions.