What is the main purpose of shampooing the hair before many services?

The main purpose of shampooing is to cleanse the hair and scalp, removing dirt, excess oil (sebum), perspiration, and product buildup so the hair is clean for the service that follows. A clean scalp and hair allow subsequent services and products to work properly. Shampoo formulas vary (clarifying, moisturizing, color-safe, etc.) to suit different hair conditions and goals. The cosmetologist selects an appropriate shampoo based on the hair analysis. Understanding the cleansing purpose of shampoo and how to choose one is basic hair-care content.