Yes, hyaluronic acid is safe and beneficial for chemically treated hair. According to Dr. Chambers-Harris, “Whether your hair has been colored, relaxed, or treated with keratin, hyaluronic acid can help restore moisture and improve its overall health. Hyaluronic acid has a positive effect on chemically treated hair because it can improve elasticity, is non-irritating and non-reactive, meaning it does not interfere with the chemical treatment, it also doesn’t strip color away from color-treated hair and it helps to tame the frizz that many people with chemically treated hair experience due to the lack of moisture and compromised strand structure.