Final answer:
A skin patch test can determine if a client has a sensitivity or an allergic reaction to the chemicals used in procedures like hair coloring.
Step-by-step explanation:
A skin patch test can help determine if the client has a sensitivity or an allergic reaction to the chemicals being used. This is important in procedures like hair coloring, where the client's skin may come into contact with certain chemicals. By applying a small amount of the chemical to a patch of skin and observing any reactions, the test can help identify any potential issues and prevent adverse effects.