Before applying color to the entire head, which test should you perform first to check for potential allergic reactions?

• A. Patch test
• B. Strand test
• C. Sectioning
• D. Protective barrier

Answer: (A)

Checking for allergic reactions to hair color begins with a patch test, designed to detect skin sensitization to the ingredients in the color product. Many hair colors contain substances like para-phenylenediamine and fragrances that can trigger contact dermatitis in some people, sometimes after years of use. By applying a small amount of the product to a discreet skin area, you can see if the client develops a reaction before applying color to the entire head.

To do it, place a tiny dab of the product (or a standard patch test solution) on clean skin behind the ear or on the inside of the elbow. Cover it with a patch or tape if you’re using the standard patch test method and leave it in place for 24 to 48 hours. Then check for signs of a reaction—redness, itching, swelling, or blistering. If any reaction occurs, do not proceed with the hair color and discuss alternatives or a different product with the client.

Other options serve different purposes: a strand test checks how the color will appear on the hair and how the hair reacts, rather than any potential allergy; sectioning is about distributing color evenly; a protective barrier is skin protection during application, not a test for sensitivity. So the patch test is the appropriate first step to ensure safety before full-head coloring.