Saliva is a clear fluid produced by the salivary glands that helps in digestion and protects the oral cavity from infections. Salivary gland dysfunction occurs when there is a reduced or absent secretion of saliva, which can lead to dry mouth, difficulty in chewing and swallowing, and an increased risk of dental caries and oral infections. Causes of salivary gland dysfunction include certain medications, radiation therapy, autoimmune diseases, and aging.