Photo-Illustration: The Strategist; Photo: Retailer Skin-care ingredients are popular in cycles. There was the year when everything had hyaluronic acid in it, and another when niacinamide was all the rage. Now everything has peptides in it. For example, when Rhode launched its initial product offering, each one included peptides — most had the ingredient in the name. So what even are they? And do you need them? I talked to a dermatologist and a cosmetic chemist to find out. What are peptides?