Which of the following describes a primary purpose of patch testing?

• A. Cosmetic products
• B. Sun exposure
• C. Hair dye
• D. Nutritional supplements

Answer: (A)

Patch testing is used to check whether a product may cause an allergic skin reaction before it is used. It helps identify sensitivities to ingredients commonly found in cosmetics, such as fragrances, preservatives, or dyes, so clients can avoid products that could trigger dermatitis. The test is typically applied to a small skin area under occlusion for 24–48 hours and then read for any redness, swelling, or blistering.

Cosmetic products are the best fit here because patch testing targets reactions to substances applied to the skin, which is exactly what cosmetics contain. Sun exposure involves different reactions and tests (not patch testing). Hair dye is a common cosmetic that may be tested, but the primary purpose of patch testing is to screen cosmetics in general, not just one type. Nutritional supplements are ingested and aren’t evaluated with patch testing.