What is the primary ingredient in most shampoos?

The primary ingredient in most shampoos is water. This is because water serves as a solvent that dissolves other ingredients and facilitates the delivery of cleansing and conditioning agents to the hair and scalp. Since shampoos are designed to clean and remove dirt, excess oil, and product buildup, having water as the main component allows for effective application and distribution of the shampoo when it is used.

Other ingredients like sodium chloride, alcohol, and silicone are often included in shampoos for specific purposes, such as thickening, providing texture, or improving the feel of the hair. However, these ingredients are not present in the same volume as water. The formulation aims at ensuring that the shampoo cleans effectively while being easy to spread and rinse out, which is largely enabled by water's properties.