What should be done before performing a chemical service on a client?

Conducting a patch test before performing a chemical service is essential for ensuring client safety. This test involves applying a small amount of the chemical product to a discreet area of the client's skin, often behind the ear or on the inner arm, and then observing for any adverse reactions, such as redness, itching, or swelling. This step is crucial because some clients may have sensitivities or allergies to certain ingredients in chemical products, and a patch test can help identify potential reactions before applying the product to the hair or scalp.

While reviewing the client's hair history is vital for understanding their previous treatments and setting realistic expectations, it does not directly assess the immediate risk of an allergic reaction. Preparing the chemical solutions is part of the service but does not address client safety, and allowing the client to wash their hair may not be advisable before a chemical treatment, as it could alter the hair's condition regarding product effectiveness. Therefore, the patch test is the primary and most critical step to protect the client’s health during chemical services.