No client with open sores, infectious disease or disorders of the skin, or parasitic infections will be rendered service in a shop or school, unless they have __________ from a physician.

In the context of Tennessee cosmetology regulations, the requirement for having written permission from a physician before rendering services to a client with open sores, infectious diseases, skin disorders, or parasitic infections is crucial for maintaining hygiene and safety standards within cosmetology practices.

Written permission serves as a formal document that clearly indicates the physician's assessment of the client’s condition and their approval for the service to be provided. This helps to protect both the client and the service provider by ensuring that any potential risks are acknowledged and managed appropriately. It also provides a clear record that can be referred to if any issues arise, thereby supporting compliance with health and safety regulations.

Oral permission does not provide the same level of assurance or accountability, and having insurance approval or parental consent is not relevant in this specific situation regarding dermatological conditions. Thus, written permission is the most appropriate and protective measure required by law in these circumstances.