Why is patch testing required before a color service?

• A. To determine the client's favorite shade.
• B. To decide the shade.
• C. To check for potential allergic reactions to color products.
• D. To measure porosity.

Answer: (C)

Patch testing is used to identify potential allergic reactions to hair color ingredients before applying the product to the scalp. Some dyes contain allergens that can trigger reactions like redness, itching, or swelling, so testing helps catch sensitivities ahead of time. The test is typically observed for 24 to 48 hours to ensure safety during the actual coloring service. It isn’t about choosing or confirming a shade, nor about measuring hair porosity, which are addressed by shade selection and porosity tests, respectively.