review found there was no strong evidence that topical therapies are effective in relieving the symptoms of dry mouth. cancer treatments including chemotherapy and radiation therapy may impair salivary flow. radiotherapy can cause permanent hyposalivation due to injury to the oral mucosa containing the salivary glands, resulting in xerostomia, whereas chemotherapy may cause only temporary salivary impairment. furthermore surgical removal because of benign or malignant lesions may also impair function. graft versus host disease after allogeneic bone marrow transplantation may manifest as dry mouth and many small mucoceles. salivary gland tumours may occur, including mucoepidermoid carcinoma, a malignant growth. clinical tests/investigations a sialogram is a radiocontrast study of a salivary duct that may be used to investigate its function and for diagnosing sjögren syndrome. other animals the salivary glands of some species are modified to produce proteins; salivary amylase is found in many bird and mammal species (including humans, as noted above). furthermore, the venom glands of venomous snakes, gila monsters, and some shrews, are actually modified salivary glands. in other organisms such as insects, salivary glands are often used to produce biologically important proteins such as silk or glues, whilst fly salivary glands contain polytene chromosomes that have been useful in genetic research.