"Polyhydroxy acids are a newer generation of alpha hydroxy acids," explains Guanche. "They are milder and less irritating (or stingy) when applied, but they still micro-exfoliate the skin." Since it's a larger molecule, PHAs are able to "remove the surface of dead skin cell layers without penetrating too deeply in the skin," which translates to less irritation, explains Guanche. She also notes that they're great for improving pigment, fine lines and even hydration (thanks to the fact that it's also a humectant).
Also, its gentleness makes it great for sensitive skin: "It's especially good for skin prone to rosacea and eczema and mature compromised complexions," says Lorencin.
You'll often see ferulic acid used in conjunction with vitamins C and E. "Vitamin C especially tends to be unstable in formulation, but the ferulic acid helps it maintain stability," Guanche says. "It has antioxidant effects and reduces damage caused to the skin by free radicals."
Azelaic acid is becoming more and more popular as a skin care ingredient lately, which is in part due to its effectiveness in treating "acne, rosacea and unwanted pigmentation," Guanche says. She also notes that the exfoliating acid is great for helping eradicate any mites you may have in your pores (yikes!). Similarly, Lorencin says that "it is especially effective in fighting P. Acnes bacteria," (aka one of the main causes of acne). "It is milder than salicylic acid and can be tolerated by most skin types," she adds.
