Girls are bombarded on social media with advice from influencers touting elaborate skin care routines with high-priced serums, mists and creams. But what is the right skin care routine for preteens?

Simple is best, dermatologists say. Before puberty hits, most kids only need three things: a gentle cleanser, a moisturizer and sunscreen. “That’s it. Full stop. You don’t need anything else,” says Dr ...