- very good question. The unsatisfying answer is because that’s what the regulations are.
The FDA even specifically says “Approval of a color additive for one intended use does not mean approval for other uses.” Therefore, even if a colorant is approved for food, that does not mean it is approved for cosmetics.
The cosmetic industry in the US is not highly regulated except in a couple areas. Colorants is one of those areas. Formulators (who follow the law) are limited to the colors listed in the FDA approved colorants. The safety or origin the ingredient does not matter. If it’s not on the list, it’s illegal to use as a colorant.
Thank you Dr. Perry for the clarification.
I guess it has something to do with the stability and subsequent changes of natural colorants in the formulas. As far as I’m concerned, beetroot powder and all other food/fruit/vegetable powders do not work in color cosmetics as they are. They either don’t work at all (they color the product but not the skin) or they stain the skin irreversibly (like turmeric or henna).
Natural colours are really unstable. Most change colour with pH and have been used as pH indicator solutions, those that don’t tend to have high light instability anyway.
In one formulation (this was naturally coloured fish oil softgels) the turmeric produced a beautiful shade of yellow - then bleached in barely 48 hours to white (the base colour of the softgel is titanium dioxide).
Anthocyanin colours are often used as pH indicators too. Hibiscus for example is yellow at neutral pH, green in alkalis and only red in acidic solutions.
Blue pea is blue in neutral solutions but turns pink in acidic solutions.
Beet powder is a little more stable compared with others, but it does go more pink in an acid and redder in alkali.