FD&C red #3 is an organoiodine compound, specifically a derivative of fluorone.
- Used for food colouring
- printing ink
- biological stain
- dental plaque disclosing agent
- radiopaque medium
- sensitizer for orthochromatic photographic films
- Can be used in colored food and ingested drugs in the USA without any restriction, however, its use is banned in cosmetics and external drugs. The lake variant is also banned from use in the United States.
Source: Wikipedia, https://en.wikipedia.org/wiki/Erythrosine