Which service requires a patch test before application?

Hair coloring requires a patch test before application to determine if the client has any allergic reactions to the chemicals in the dye. A patch test typically involves applying a small amount of the product to a discreet area of the skin, usually behind the ear or on the inner elbow, and observing the area for any signs of irritation or allergic response over a 24 to 48-hour period. This precaution helps to prevent any adverse reactions that could result from the application of hair color, protecting both the client and the professional.

In contrast, while services like hair bleaching and hair straightening may also involve strong chemicals, hair coloring is specifically mandated to have a patch test due to the variety of dyes and potential sensitivities individuals might have. Nail polish application generally does not require such testing, as it typically uses formulations that are less likely to cause allergic reactions in most people.