Peter Thomas Roth Skincare Serum

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The Souped-Up Antioxidant: THD Ascorbate

For decades, derms have waxed poetic about the brightening, wrinkle-smoothing, sun-protecting benefits of vitamin C, yet this wunderkind acid can also be harsh on sensitive skin. Not anymore. Unlike other topical water-soluble forms of C, like ascorbic acid or L-ascorbic acid, THD is oil-soluble, meaning it uses your skin's natural oils to penetrate deeper without irritation, says Deanne Mraz Robinson, MD, assistant clinical professor of dermatology at Yale New Haven Hospital. "Research has found that THD increases collagen and reduces melanin production while working as a potent antioxidant to protect against UV and environmental stresses." Bonus: Unlike other forms of C, THD is stable at lower, nonirritating concentrations, so you can truly give your skin the kid-glove treatment.

Find it in: Peter Thomas Roth Potent-C Power Serum ($98;