What it is
CI 42090 is a triarylmethane synthetic dye that provides a bright blue color, identical to the colorant known as Blue 1 or Brilliant Blue FCF. In sunscreens it is used in very small amounts to neutralize yellow tones, support tone-up shades, or give a tinted, color-correcting finish. It is highly water-soluble and present only at trace levels needed to achieve the target shade.
Safety & warnings
CI 42090 is a long-established regulated cosmetic colorant with low irritation potential at the trace levels used for tinting. As a water-soluble dye it is not comedogenic and is not a fragrance allergen.
Origin & sourcing
Synthetic; manufactured by organic synthesis as a triarylmethane dye.
Questions everyone asks
Is CI 42090 the same as Blue 1?
Yes. CI 42090, Blue 1, and Brilliant Blue FCF all refer to the same synthetic blue dye.
Why is a blue dye in a tone-up sunscreen?
A trace of blue helps counteract yellow tones and create the corrected, brightened cosmetic finish these products aim for.