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I stumbled across an ad for a clear, colorless lip balm that purportedly tints your lips a shade of pink determined by your skin's pH.

This balm stain applies on clear then reacts with your skin's pH levels, uniquely creating the perfect shade of pink lips just for you.

Out of curiosity (and the fact that I'm an easy target for marketing), I read further. The product contains the following ingredients:

  • Hydrogenated Polyisobutene
  • C12-15 Alkyl Benzoate
  • Diisostearyl Malate
  • Octyldodecanol
  • Dibutyl Iauroylflutamide
  • Dibutyl Ethylhexanoyl
  • Thylhexanoyl Glutamide
  • Isononyl Isononanoate
  • CI 45410
  • Chrysanthemum (a whole flower added to the bottom of the tube, presumably just to make it look nice.)

Other than CI 45410, I can't find anything on the above list that mentions anything about color -- and there's nothing listed that I think could change color based on pH.

Note: Some of the ingredients are very hard to find data for, but most seem to be thickening agents.

Does this clear lip gloss actually have the ability to change color based on pH or does the color come from the CI 45410? If it's from the CI 45410, what causes it to go from clear to pink?

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  • $\begingroup$ I will hazard a guess here. It would be easy for you to confirm or falsify this guess. Looking at the ingredients (some of which have had their names/spelling mutated beyond recognition) I suspect this question is equivalent to the question: "If water is transparent, why is snow white?" That is, the pigment (or dye, not sure) Red 27 Lake isn't going to become not red at any remotely reasonable skin pH. So, the only explanation I can think of is that the red is obscured by the presence of liquid crystals. Those could be (mildly) sensitive to pH but are [con't below] $\endgroup$ – alphonse Aug 10 '17 at 22:32
  • $\begingroup$ en.wikipedia.org/wiki/Phloxine $\endgroup$ – Mithoron Aug 10 '17 at 22:45
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    $\begingroup$ [con't] far, far, far more likely to be temperature sensitive. This is just speculation on my part, but I suspect the lc phase is simply acting as a light scatterer rather than changing the absorption wavelengths and that the amount of lc is highly sensitive to temperature near the temperatures of skin (lips). $\endgroup$ – jonsca Mar 20 at 22:36
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CI 45410 (A.K.A. Phloxine B or acid red 92) is a pH dependent dye which is clear below about pH=4.1 and pink at pH>4. The formulation is mildly acidic and is neutralised by saliva upon application to become pink.

(Thereby "uniquely creating the perfect shade of pink lips just for you.")

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