What must be done before applying hair color?

Performing a patch test for allergies is a crucial step before applying hair color. This test is designed to identify any potential allergic reactions to the hair dye, which can include symptoms like itching, redness, or swelling on the skin. By conducting this test 24 to 48 hours prior to the hair coloring process, professionals can ensure the safety of the client and prevent any adverse reactions when the color is actually applied.

While washing the hair with shampoo, using a conditioning treatment, or buzzing the hair might be part of a salon's routine practices, they do not specifically address the safety aspect that the patch test covers. Ensuring that a client is not allergic to the hair dye being used is a fundamental procedure for every hair coloring application.