During a chemical service, which must be done before applying the product?

Before applying a chemical product during a service, conducting a patch test is essential. This test serves as a precautionary measure to evaluate how a client's skin will react to the chemicals being used. It involves applying a small amount of the product to a discreet area of the client's skin, typically behind the ear or on the inner arm, and observing for any adverse reactions, such as redness, swelling, or irritation, over a specified time period.

This step is vital because it helps prevent allergic reactions and ensures the safety and comfort of the client during the chemical service. If a patch test is not performed, there's a risk of a severe allergic reaction, which can lead to significant complications.

In contrast, while shampooing and conditioning may play valuable roles in preparing the hair for chemical services, and applying a serum can enhance the hair's health during treatments, they do not address the safety concerns related to skin reactions. Therefore, the patch test stands out as a necessary preliminary procedure before any chemical product application.