A cream begins to pill under sunscreen. A serum changes color after storage. A new raw material creates an unusual odor. Customers complain that a product feels different even though the ingredient list has barely changed.
The natural reaction is often to replace one ingredient.
But cosmetic formulas rarely fail because of one ingredient acting alone.
An emulsifier may be incompatible with the oil phase. Two thickeners may compete with each other. A preservative may react with an active ingredient. A supplier may change the carrier system of a raw material without changing its INCI name.
