Chirality is the idea that every molecule has two sides and that each side is the mirror image of the other. Flaherty says, “It’s similar to the way that you have a left and right hand, and they fit together in a handshake. The sides have similar functions, but they operate in a slightly different way.”
Flaherty says, “Our skin cells all have receptors on them and the receptors tell the cell how to react: it could tell your skin to inflame, to calm down, to itch.” When you have an ingredient molecule that has been chirally purified, or separated into its two sides, you can then pick the side of the molecule that will best match the skin’s receptor. “With an ingredient like Vitamin C, or Absorbic Acid, it can lead to problems if it’s not chirally purified,” says Flaherty. “You’ll usually see skincare ingredients use L-Absorbic Acid, meaning the left side of the molecule."
“One side of the molecule will fit in the receptor and the other side needs to go somewhere, so it just hangs out on the skin,” says Flaherty. This can cause of irritation and sensitivity because “the skin doesn’t know what to do with that other side of the ingredient,” Flaherty explains. In fact, the FDA has mandated that all pharmaceuticals have to be chirally purified so that the ‘hanging out’ sides of the molecules don’t interfere with bodily functions. In the case of skincare, Flaherty says, “using chiral technology allows us to make a more effective product without irritating the skin.”
Chiral or Bust?
Not all ingredients have to be chirally purified—for example, many essential oils don’t need to be separated. But more advanced technical ingredients like lactic acid or salicylic acid, really should go through the purification process. Look for ingredients with L- or D- in front of them — this indicates which side of the molecule is being utilized. Hint: If the ingredient has both L- and D- listed, then it’s using both sides of the molecule and they’re just trying to trick you with fancy marketing!