Foundation turning darker or more orange over the course of wear is a real chemical reaction between iron oxide pigments and skin sebum, not a quality issue. Here is the actual chemistry behind it.
I wore the wrong foundation shade for two years because I tested it on my hand and decided in thirty seconds. Here's what oxidation actually is, and what changed once I started testing properly.
Foundation is the most personal product in makeup — and the one most people are wearing wrong. Here's the complete guide to formulas, finishes, skin types and the 7 best foundations of 2026.