Hydroquinone —
A Supervised Course, Not A Daily Habit

Hydroquinone (1,4-dihydroxybenzene) blocks tyrosinase, the enzyme pigment cells use to make melanin, and is toxic to overactive pigment cells. Excess pigment lightens over weeks to months. It does not stop pigment returning, so sun protection and gentler maintenance follow any course.

Hydroquinone has decades of clinical use, and newer lighteners are often measured against it. Published analyses support its effect on epidermal pigment while flagging the risks of long or unsupervised use. It does not reach dermal pigment, such as Hori's naevus, which is why the pigment type is identified first; see facial pigmentation types.

It is prescribed for a course of a few months, then reassessed. If the pigment has improved, it is tapered or paused and a gentler agent takes over. If it has not, the diagnosis is reconsidered rather than the cream extended. Doctors sometimes combine it with a retinoid and a mild corticosteroid, and it sits within a wider plan for melasma.

• Anyone without medical supervision.
• Pregnancy or breastfeeding, unless a doctor advises otherwise.
• Broken or inflamed skin.

Irritation can trigger more pigment, especially in darker skin, and sensitive skin can develop contact dermatitis. With long, high-strength or unregulated use, exogenous ochronosis, a blue-grey or blue-black darkening on the cheeks, temples and jaw, can develop and is hard to reverse. Use it with daily sunscreen, add one new active at a time, and stop if irritation appears.

Hydroquinone is not permitted in cosmetic products in Singapore and is a prescription-only medicine, supplied through a doctor. The HSA has repeatedly warned about imported whitening creams found to contain undeclared hydroquinone or mercury, so lightening creams from online shops or salons should be avoided.