Hydroquinone

Prescription depigmenting agent that inhibits melanin production.

Also known as: 1,4-Benzenediol, hydroquinone monobenzoyl, same name.

What it is

Hydroquinone is a small-molecule phenolic compound that directly inhibits tyrosinase, the enzyme responsible for melanin synthesis. It is available over-the-counter at 2% concentration in most markets, and by prescription at 4% and higher.

What it does

Hydroquinone reduces melanin production by blocking tyrosinase activity and promoting melanin degradation. It lightens existing hyperpigmentation, melasma, post-inflammatory hyperpigmentation, and age spots with consistent use over 4–12 weeks. Results are visible but reversible; pigmentation typically returns within months of discontinuation.

The evidence

Strong clinical evidence supports hydroquinone's efficacy for melasma and post-inflammatory hyperpigmentation; multiple RCTs confirm 4% formulations outperform 2% and placebo. Mechanism is well-established; long safety record in dermatology, though concerns about ochronosis with prolonged use at high concentrations have emerged in some populations.

Best for

Melasma, post-inflammatory hyperpigmentation, age spots, and uneven skin tone in all skin types; particularly effective in darker skin.

Pairs well with

Tretinoin, glycolic acid, vitamin C, sunscreen (essential). Combination with retinoids and AHAs enhances penetration and efficacy.

Use cautiously with

Benzoyl peroxide (oxidizes hydroquinone and reduces efficacy). Use cautiously with other depigmenting agents (kojic acid, arbutin) without medical guidance; avoid in pregnancy without physician approval.

Cautions

May cause irritation, dryness, and contact dermatitis in sensitive skin; sun exposure can reverse results and worsen pigmentation. Prolonged use (>3–4 months) at high concentrations carries a small risk of ochronosis (blue-black discoloration), especially in darker skin tones; use under medical supervision and take periodic breaks.