Note: All content and information in this article are for information purposes only. You should consult a medical professional prior to starting new skincare regimens.

Over the past few years, serums have skyrocketed in popularity—and rightfully so. The buzzy formulas address a myriad of skincare concerns, from brightening (looking at you, vitamin C) to minimizing the appearance of fine lines and wrinkles (retinol to the rescue!). Even better: you aren’t limited to just one. Want to learn how to layer ‘em on? You’re in luck… Shopbop got the scoop from the best in the biz: we’re talking renowned dermatologists & brand founders. Read on to learn the most effective way to—as the pros say—cocktail your formulas.

Why do pros recommend using more than one serum? “You want to maximize the product benefits such as firming, brightening, and smoothing at each living skin layer,” Dr. Loretta explains. But as a best practice, the dermatologist suggests sticking to two formulas. “When we start to layer three or four serums, there is a chance that they will dilute or counteract some of the benefits of each other.” Both dermatologists advise against mixing certain ingredients as they could potentially irritate the skin. For instance, Dr. Loretta says to avoid combing tretinoin with alpha hydroxy acids (think chemical exfoliants like glycolic, lactic, and mandelic acids). Dr. Gross agrees, explaining that tretinoin on its own can be harsh and not suitable for all skin types. “Adding glycolic acid [as well as other AHAs], can lead to red, inflamed skin.”