CI 26100
Explained
CI 26100 is a synthetic red dye that does exactly one job: it makes a product look red.
It is oil-soluble rather than water-soluble so you'll find it in oily formulas like nail products, hair oils, or oil-based cosmetics.
On concentrations, neither the EU nor the FDA sets a hard number. The EU allows it with purity limits on leftover manufacturing residues and the FDA allows it in externally applied cosmetics at levels consistent with batch-certified good manufacturing practice.
Industry reports around 0.5% concentration usage in leave-on products, but most products use far less because it's a pretty strong dye.
The one rule that both regions share is that it isn't allowed anywhere it would touch mucous membranes (so no lipstick or eye products).
That restriction comes from an unresolved 2005 EU data request on how much of the dye penetrates skin and breaks down there, and not from any reported consumer harm.
Allergy risk is low and a guinea pig study ranked it a much weaker sensitizer than common hair-dye chemicals. But the same study found animals sensitized to paraphenylenediamine sometimes cross-reacted to it, so it's worth flagging for a patch test if you have a known permanant-hair-dye allergy.
See all 134 products with CI 26100
