The Science Behind Color-Changing Makeup

This story originally appeared on Allure. 

Between M.A.C.'s latest lip balms and Lipstick Queen's highly obsessable Frog Prince collection, color-changing cosmetics are having a moment—and we're having some major '90s makeup flashbacks. But how do these transforming pigments actually work?

While lots of modern color-changing products emphasize high-tech jargon about body chemistry and your natural pH, the technology behind color-changing makeup is nothing new. In fact, one of the most commonly used ingredients for a color presto-chango has been around for decades: Red 27.

Its magical properties live in its formulation. "Red 27 is pH-driven," says cosmetic chemist Ni'Kita Wilson. "When it comes in contact with moisture, the change in solubility and pH causes the dye to turn bright pink." As long as it isn't exposed to water, the dye is colorless and can be mixed into an oil- or a wax-based product (such as lip balm) without adding its own bright shade. In turn, that product can remain clear or be dyed an array of wild colors, like Lipstick Queen's funky green blush. The amount of Red 27, along with the other dyes used, primarily determines the final shade.

Does that mean color-change makeup products don't yield the perfect custom shade for you based on your pH? Yes and no. "Red 27 can turn based on your pH or the pH of its surrounding environment," says Wilson. Since practically everyone's skin has a pH of around 5, your chemistry-based shade has more to do with your natural skin tone mixing with the Red 27's bold pink than some technological marvel. Does that make it any less satisfying to watch your friends' expressions as you whip out a bright green lipstick over brunch? Not in our book.