Tested on animals:Yes
This water-based serum is said to lighten dark spots with vitamin C. Although there’s vitamin C in this serum (a novel form, explained below), the formula contains a potentially problematic amount of alcohol and also comes in clear packaging that won’t keep the vitamin C stable during use (see below for details). What was Kiehl’s thinking? Alcohol causes dryness, free-radical damage, and hinders skin’s ability to look and act younger.
Vitamin C, either as pure ascorbic acid or as the derivative that Kiehl’s uses (3-O ethyl ascorbic acid, which breaks down to pure vitamin C on skin) is a wonderful antioxidant and there’s a good amount of research showing how it helps reduce dark spots and other brown discolorations on skin, most of which comes from sun damage. But because all forms of ascorbic acid are susceptible to deteriorating in the presence of light and air, opaque packaging is a must. A clear bottle just doesn’t cut it. The China-based company that supplies this form of vitamin C to cosmetic lines has their own research showing this ingredient is stable after 90 days of light and air exposure but without seeing the study, it's difficult to know the control factor, not to mention that the company selling this ingredient to cosmetic firms likely won't go on record claiming it's unstable.
This somewhat tacky-textured serum also contains fragrant lavender oil, a plant oil that even in small amounts can cause irritation that hurts skin’s ability to repair itself and generate healthy collagen. The citrus extracts this contains aren’t good news for your skin, either.
As for the peony root extract that Kiehl’s promotes for this skin lightening product, it has no established benefit for skin. Even if it did, the amount this serum contains is minuscule.
Clinique, Philosophy, and Paula’s Choice are among the brands that offer superior skin lightening products that stand a great chance of lightening dark spots. You can find them all on our Best Skin-Lightening Products list!