If you have multiple concerns, you might want to use multiple formulas. “I recommend treating different areas with different products,” Mattioli says. “Maybe you’ll use a vitamin C serum all over but then dab on [another] for hyperpigmentation on just a few spots.” Just run any combination by your dermatologist to avoid any potential reactions.
To save time, don’t try mixing a serum into your moisturizer. This “lessens the ability of the serum to absorb effectively,” Dr. Nazarian says. “Products should be applied one by one.”
Not all serums are applied with the same frequency. “This varies with the ingredients,” Dr. Nazarian says. “I prefer antioxidants in the morning because they give you additional protection from the environment, and most of us don’t use enough sunscreen as is,” Mattioli says. Yet certain ingredients are best when slathered on at night. For example: “Retinols are not sun-stable and will degrade if applied in daytime,” Dr. Nazarian explains. Bottom line: Read the label instructions carefully.