What is the primary reason for performing a patch test before coloring hair?

Performing a patch test before coloring hair is primarily done to identify potential allergies. This precaution is crucial because many hair coloring products contain chemicals that can cause allergic reactions in sensitive individuals. By applying a small amount of the dye on a discreet area of the skin, typically behind the ear or on the inside of the elbow, the stylist can monitor for any adverse reactions such as redness, itching, or swelling. This test helps ensure the safety of the client and prevents potentially serious allergic responses during the actual hair coloring process. It is a standard practice in the beauty industry to promote client welfare and uphold professional standards.