I have been corresponding with the Director of Color Certification & Technology Division at the FDA regarding exactly what is legal to use in Bath Bombs specifically. We (at Mad Micas) carry Batch Certified Lakes and we carry neon pigments. There seems to be some confusion regarding whether the use of neons in bath bombs is within the FDA regulations.
These are my findings:
Bath bombs, bath salts and nail polish are regulated as cosmetics so they should only contain FDA approved color additives. You must check the uses and restrictions for each approved color additive. Refer to the list of approved color additives. If you don’t see the color on this list it is not permitted in the U.S.:
If the color additive is only allowed for external use, then it is not allowed in lip products or bath salts/bombs. Please see the definition of external use in the Code of Federal Regulations Title 21 Part 70.3(v):
§70.3 Definitions.……(v) The terms externally applied drugs and externally applied cosmetics mean drugs or cosmetics applied only to external parts of the body and not to the lips or any body surface covered by mucous membrane.
Regarding neon pigments or other pigment blends:
If the dye or lake, such as Yellow 5, Red 28, Red 40, etc. is not from a certified lot, then the pigment blend is not permitted in FDA regulated products. It may be okay in Europe or Asia, but in the U.S. it is not allowed.
In layman's terms, if you use an approved color additive in your bath bomb, it must be batch certified. Period. Neons are not permitted at all unless the blend uses FDA batch certified dyes or lakes.
Micas, on the other hand, are not regulated by the FDA even if they are cosmetic grade and can be used in any bath products. Cosmetic micas can be used in cosmetics depending on their ingredients (depending on if they are lip and eye safe, etc.)
I hope this has cleared up some fuzzy areas when making bath bombs or nail polish for sale and staying within the FDA regulations regarding these products.