Hair and Scalp Care Practice Test 2026 – The Complete All-in-One Guide for Exam Success!

Shampoo is built around a water-based base, with purified water serving as the solvent that carries all the other ingredients. Water typically makes up the largest portion of the formula by weight, providing the medium in which surfactants and additives are dissolved or dispersed. The cleansing action comes from the surfactants, which are essential but generally used in a smaller portion than the water. Fragrance and preservatives are included for scent and shelf life, respectively, and appear in even smaller amounts. So the main ingredient is purified water because it provides the solvent foundation for the whole product.