What must all barbers do before applying any chemical treatment?

Before applying any chemical treatment, conducting a patch test is essential for barbers to ensure the client's safety and to identify any potential allergic reactions to the chemicals involved. A patch test involves applying a small amount of the chemical solution to a discreet area of the client’s skin, usually behind the ear or on the inner arm, and waiting for a specified period to observe for any adverse reactions, such as redness, itching, or swelling.

This practice is crucial not only for the health and comfort of the client but also helps the barber uphold professional standards in their services. While observing the client’s hair condition is important for determining the most suitable treatment, and explaining the product to the client can enhance their understanding and confidence, these actions do not address the immediate health and safety concerns that the patch test specifically resolves. Additionally, performing a haircut prior to chemical application is not universally necessary and can depend on the specific services being offered. Thus, the patch test is the correct and vital step that must be taken before any chemical treatment is applied.