5.3. Product Knowledge and Cosmetic Chemistry

💡 First Principle: Every product you apply to a client's skin has a formulation designed to interact with the skin in a specific way. Understanding basic chemistry — pH, active ingredients, how different categories of ingredients work — allows you to select appropriate products and avoid harmful combinations.

The exam tests foundational cosmetic chemistry: what pH means for skin and products, how major ingredient categories function, and why product compatibility matters.

⚠️ Common Misconception: "Natural" or "organic" products are always safe for sensitive skin. Many botanical ingredients — essential oils, plant extracts, even citrus compounds — contain potent chemicals that cause contact dermatitis in some clients. The origin of an ingredient does not determine its safety; its interaction with that client's skin does.