Because the skin on your back is thicker than facial skin, postinflammatory hyperpigmentation—the dark spots that linger after a zit heals—in that area takes longer to fade, say Dr. Sherber. At the first sign of a spot, treat swelling and redness with salicylic acid (Clean & Clear contains 2 percent) to prevent scarring. If you’ve picked at it and have a stubborn older mark, apply a brightening serum to correct excess pigment. (SkinMedica’s can help fade your dark marks in as little as two weeks.)nbsp;