Thiamidol treats the underlying cause of hyperpigmentation by reducing melanin synthesis in the skin, causing existing dark spots to disappear and new dark spots to develop less often. Thiamidol, the active ingredient in the Eucerin Even Pigment Perfector line, has been scientifically and dermatologically shown to eliminate dark spots and prevent their recurrence. The first benefits are noticeable after two weeks and continue to improve with continued use.