Serena Williams' Esthetician Started a Skincare Line — and We Tried It First

"A lot of people don't like heavy moisturizer, because it messes with your pH. Especially in Summer, you want something light." That's why Guidi recommends layering Give Me A Boost, a hyaluronic acid serum, under a lighter moisturizer. "It's great for those with acne or eczema-prone skin who are afraid of an intense moisturizer," she said.

Shop: Give Me A Boost ($30)