Hydroquinone 4% is a topical depigmenting cream used for melasma, post‑inflammatory hyperpigmentation, sun spots, and freckles by inhibiting tyrosinase to reduce new melanin synthesis and gradually lighten dark patches over weeks to months with strict daily photoprotection. Best practice is thin, even application to affected areas once or twice daily for limited courses, pausing if no improvement by 2–3 months and cycling to minimize complications, often combined with sunscreen and, when prescribed, retinoids or triple‑combination formulas for stubborn cases. Patch testing and dermatologist guidance optimize outcomes and safety.