While both exfoliate at the chemical level, they do so in slightly different ways. First up: Enzymes are tiny molecules found in fruits (think pumpkins, cherries, and papaya) that break down keratin—aka, the protein in dead skin cells. They get rid of those dead skin cells at the surface of the skin, but they don’t exactly promote cell turnover for living cells underneath. Think of enzymes as shedding already dead skin and buffing it smooth rather than a forced cell turnover.
On the flip side, acids penetrate deeper into the skin and accelerate turnover for all your skin cells, not just the dead skin sitting up top: “Acids physically turn over the skin cells (which can cause the actual shedding of the skin), which allows new skin cells to generate,” says celebrity esthetician Lisa Guidi, owner of Erase Spa. While also found in natural, plant-based products (lemon, apple cider vinegar, and the like), acids lend a bit more intense exfoliation than the average fruit enzyme.
“Imagine that there is glue between skin cells, keeping them together,” explains double board-certified dermatologist Melynda Barnes, M.D., clinical director for Rory—an online health care service that creates customizable skin care formulas. “Enzymes break down that glue (the keratin protein), which allows the dead skin cells to be removed or exfoliated from the skin.” Acids, on the other hand, “work by triggering cell death in older skin cells and promoting new skin cells to grow. This results in older cells sloughing off and newer skin cells taking their place.”