Ferric ammonium ferrocyanide
EWG Skin Deep Hazard Score:
What is it:
Ferric ammonium ferrocyanide is a synthetic colorant used to impart a blue color to cosmetic formulas. It is closely related to Fferric ferrocyanide, or Prussian Blue, but is not the same chemical. It belongs to a class of chemicals called inorganic cyanides and is also a quaternary ammonium compound.
What are its risks:
- According to this safety sheet, "Inorganic cyanides react slowly with water to evolve gaseous hydrogen cyanide (HCN). Acids cause the rapid evolution of HCN; carbon dioxide from the air is sufficiently acidic to liberate HCN from solutions of cyanides." Hydrogen cyanide is a highly toxic gas. Would the water in sweat plus exposure to air, combined with the compound in a makeup be able to create enough toxic gas to be harmful? Likely not, but it could cause an unknown low-level exposure.
- The safety sheet linked to above also sates that if exposed to skin it can be a potential irritant. While some safety sheets aren't an accurate reflection of the safety of an ingredient in cosmetic use, the following phrase really is concerning: "If symptoms such as redness or irritation develop, IMMEDIATELY call a physician and be prepared to transport the victim to a hospital for treatment." and in cases of ingestion: "IMMEDIATELY call a hospital or poison control center and locate activated charcoal, egg whites, or milk in case the medical advisor recommends administering one of them. [...] IMMEDIATELY transport victim to a hospital. If the victim is convulsing or unconscious, do not give anything by mouth, assure that the victim's airway is open and lay the victim on his/her side with the head lower than the body." These strong warnings would indicate to me this ingredient has at least moderate toxicity.
- According to this study, Ferric Ammonium Farrocyanide is known to be neurotoxic to humans.
- Is considered an air pollutant by the EPA. (Source)
This ingredient has been used and approved for cosmetic use since the 1970s. In small doses (not much is needed to give color to a product) it is likely not harmful. However, if one is striving to reduce their exposure to toxins as much as possible, this ingredient would be one to avoid.