What it is
Yellow 4 is a synthetic azo dye used as a cosmetic colorant to give products a yellow tint. It is highly water-soluble and is added at very low concentrations purely for aesthetic color, with no functional role in sun protection. In tone-up sunscreens it can contribute to the formula's visible shade or to color-correcting effects.
Safety & warnings
Used at very low levels as a colorant and generally well tolerated on skin. Tartrazine-type azo dyes are more noted for sensitivities when ingested than when applied topically. The dye can stain, and as with any colorant, individuals prone to reactions to synthetic dyes may prefer to patch test.
Origin & sourcing
Synthetic; an azo-class organic dye manufactured industrially.
Questions everyone asks
What does yellow 4 do in a sunscreen?
It is a colorant added at trace levels to give the product a yellow shade or support tone-up color; it does not provide UV protection.
Is yellow 4 the same as tartrazine?
Yes, Yellow 4 corresponds to the azo dye commonly known as tartrazine (CI 19140).