Sources starting with H

• Hakozaki — Niacinamide and Cutaneous Pigmentation

  This British Journal of Dermatology abstract reports niacinamide pigmentation findings relevant to cautious, appearance-focused tone-evening claims.

• Herman 2013 — Caffeine's mechanisms of action and its cosmetic use

  Peer-reviewed review describing caffeine skin penetration, cosmetic use, antioxidant properties, and effects on cutaneous microcirculation.

• Hughes 2013 — Sunscreen and Prevention of Skin Aging: A Randomized Trial

  A peer-reviewed randomized trial published in Annals of Internal Medicine in 2013 that compared daily broad-spectrum sunscreen use against discretionary use in adults under age 55.

• Hyaluronic acid: A key molecule in skin aging

  Review discussing hyaluronic acid in skin, water-binding, and skin-aging context.