Hydroquinone

Also known as: HQ, skin-lightening/depigmenting agent

Dermatology

In plain English

Hydroquinone is the most studied prescription cream for fading dark patches such as melasma and post-inflammatory hyperpigmentation. It lightens skin by reducing pigment production. It works best in short, supervised courses (often paired with a retinoid and a mild steroid) rather than continuous long-term use, and diligent daily sunscreen is essential. Overuse, especially at high strengths for long periods, can cause a paradoxical darkening called ochronosis.

The science

Hydroquinone inhibits tyrosinase, the rate-limiting enzyme of melanogenesis, and is cytotoxic to melanocytes, decreasing melanin production. It is commonly compounded at 4-6% and is the active in Kligman-type triple combinations with tretinoin and a corticosteroid, which have strong evidence in melasma. Because efficacy plateaus and risks rise with prolonged use, guideline practice favors defined treatment cycles.

References

• Ishack S & Lipner SR, Int J Dermatol 2022 (hydroquinone-associated ochronosis, systematic review)
• Bhattar PA et al., exogenous ochronosis review, Indian J Dermatol 2015