For brighter, firmer skin. It changes your skin impression. From shadow to light. From yin to yang. The whitening active ingredient 4MSK* inhibits melanin production. 4MSK*, an active whitening ingredient, inhibits melanin production and quickly penetrates into the inner layers of the skin (stratum corneum) for a whitening effect. Whitening active ingredient 4MSK (potassium salt of 4-methoxysalicylic acid) * Whitening means suppressing the production of melanin and preventing it from turning into spots and freckles.