Brushing the hair before a shampoo or chemical service is generally:

Brushing before a regular shampoo helps loosen debris and distribute natural oils, but before a chemical service the cosmetologist should avoid vigorous brushing or scratching that could irritate or abrade the scalp, since broken or irritated skin can react badly to chemicals. In general, the scalp should be intact and undisturbed before applying strong chemicals. Knowing when brushing helps and when it should be limited — especially protecting the scalp before chemical work — reflects the careful, safety-minded approach the exam rewards.