Vitamin A derivatives like retinol and retinoids — and alpha hydroxy acids (AHAs) like glycolic acid — are a dermatologist’s go-to for anti-aging. They speed skin cell turnover and increase collagen production for glowy, fine line–free skin. Using them together, however, does not have the same effect. Because they both exfoliate the outer layer of skin, “they possess potentially irritating side effects, especially in combination,” says Elizabeth Bahar Houshmand, MD, a double-board-certified dermatologist in Dallas.
When skin shows signs of irritation (think: red, stingy, flaking, and peeling), you’re less likely to stick to the regimen. You don’t have to choose one or the other. She advises patients to use these topicals on alternate days (AHA on Monday, retinoid on Tuesday, and so on).