How to test for scalp sensitivity before hair coloring, and how can stylists reduce the risk of allergic reactions and mishaps?

When I encounter a client with a sensitive scalp before coloring, I no longer just ask, 'Have you colored your hair before?' Just because someone was fine in the past doesn't mean they will be this time, especially if they've been staying up late, scratched their scalp, recently bleached their hair, or used anti-dandruff treatments—all of these can change their reaction. I usually start by…