Final answer:
Temporary hair color does not require a patch test before application because it sits on the hair's surface and is less likely to cause allergic reactions. However, it's still advisable for individuals with sensitive skin or allergies to perform a patch test.
Step-by-step explanation:
The hair color that does not require a patch test before application is temporary hair color. One of the key reasons is that temporary hair colors, such as those that wash out after one shampoo, typically sit on the hair's surface and do not penetrate the hair shaft or scalp. As a result, they are less likely to cause allergic reactions. It is important to note, however, that while a patch test may not be required for temporary hair color, individuals who have sensitive skin or a history of allergic reactions should still consider performing a patch test. Permanent and demi-permanent hair colors, which penetrate the hair shaft and often contain potentially allergenic substances like paraphenylenediamine (PPD), almost always require a patch test at least 48 hours before application to ensure that the person is not allergic to any of the product's ingredients.