Final answer:
Always test the water temperature on the inside of the wrist to ensure it is safe and comfortable for client use in a professional setting.
Step-by-step explanation:
As a precaution, you should always test the water temperature on the inside of your wrist before applying to a client's hair or scalp. The inside of the wrist is a sensitive area that can accurately gauge temperature without risking scalding or discomfort that might occur if the water is too hot. By testing the water temperature this way, you ensure that it is safe and comfortable for the client, maintaining a professional standard of care.