When should hands be washed according to sanitation guidelines?

The correct answer reflects established sanitation guidelines that emphasize the importance of maintaining hygiene between services. Hands should be washed between each client interaction to prevent the transfer of bacteria, germs, or contaminants from one client to another. This practice is crucial in esthetics to ensure the safety and well-being of clients, as well as the professional providing the service.

Washing hands only before applying makeup or solely after lunch breaks does not address the necessity to uphold sanitary conditions continuously throughout the day, particularly after interacting with different clients. Moreover, while it is essential to wash hands when they become contaminated, it is equally important to adopt a routine practice of washing hands consistently between each service to mitigate any risk of cross-contamination.