Much like vitamin C, retinol (or retinoids, retinoic acid, or Retin-A), is a favorite ingredient for skin care professionals thanks to its renowned efficacy. It also works to help even skin tone twofold.

First up: Retinol spurs collagen production: "Retinol binds to retinoid receptors within skin cells," says board-certified dermatologist Joshua Zeichner, M.D. This "activates genes that upregulate collagen production."

Second, it also increases cell turnover at the cellular level. "Besides stimulating production of new collagen, retinol enhances cell turnover," says Zeichner. "This means it sheds dead and damaged cells that make the skin look dull." And while retinol thickens the lower layers of the skin, he says, it thins out the top layer (the stratum corneum), which creates a dewy glow.

Retinol, however, tends to have less tolerability, although modern formulas are usually more gentle and sophisticated. Adding one to your routine usually takes an adjustment period where the skin may experience peeling, flaking, redness, and dryness. Some with highly sensitive skin are never fully able to tolerate the ingredient, while others will do so quickly.

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7 Derm-Approved Tips To Even Your Skin Tone (You'll Seriously Glow!) - mindbodygreen.com