Hydroquinone is an aromatic organic compound that is a type of phenol, a derivative of benzene. In medical literature Hydroquinone is considered as one of the most effective primary topical ingredient for inhibiting melanin production in melanogenesis. It is considered the golden standard for treatment of hyperpigmentation, with over 50 years of efficacy and safety data. Hydroquinone is also found naturally in many plants, some mushrooms, as well as in wheat, coffee, tea, beer, wine, berries but is detoxified within the liver into inert compounds. Its components have potent antioxidant abilities. Hydroquinone is a strong inhibitor of melanin production, meaning that it prevents dark skin from making the substance responsible for skin color. Hydroquinone does not bleach the skin but lightens it, and can only disrupt the synthesis and production of melanin hyperpigmentation.
Mechanism of action: Hydroquinone produces reversible lightening of the skin by interfering with melanin production by the melanocytes. It works by decreasing the production and increasing the breakdown of melanosomes (melanin pigment granules) in the skin's pigment cells (melanocytes). It does this by inhibiting the activity of tyrosinase, the enzyme needed to make melanin.Specifically, inhibition of the enzymatic conversion of tyrosine to DOPA (dihydroxyphenylalanine) results in the desired chemical reduction of pigment. Ultimately, this causes a decrease in the number of melanocytes and decreased transfer of melanin leading to lighter skin.
The 2% hydroquinone is readily available over the counter in various cosmetic preparations. Evidence of improvement with hydroquinone (monotherapy) is usually observed at 4-6 weeks, with improvement appearing to plateau at approximately 4 months. For better efficacy, hydroquinone is compounded into various mixtures for the treatment of hyperpigmentation. The original Kligman formula involves compounding 5% hydroquinone with 0.1% retinoic acid and 0.1% dexamethasone in a hydrophilic ointment base. Tri-Luma is a popular combination skin-lightening agent that contains 0.01% fluocinolone, 4% hydroquinone, and 0.05% tretinoin in a cream formulation. Despite the remarkable overall safety of hydroquinone, bear in mind the potential adverse effects. Contact dermatitis occurs in a small number of patients and responds promptly to topical steroids. An uncommon, yet important, adverse effect of hydroquinone is exogenous ochronosis. This disorder is characterized by progressive sooty darkening of the skin area exposed to hydroquinone. Histologically, degeneration of collagen and elastic fibers occurs. This degeneration is followed by the appearance of characteristic ochronotic deposits consisting of crescent-shaped, ochre-colored fibers in the dermis. Exogenous ochronosis has generally been observed in black patients who have used high concentrations of hydroquinone for many years. Cases occurring after the use of 2% hydroquinone have also been reported, but assays of some of these products found that they actually contained much higher concentrations. An exogenous ochronosis due to hydroquinone has been reported from South Africa. For this reason, the general recommendation is that hydroquinone should be discontinued if no improvement occurs within 4-6 months. Hydroquinone-induced ochronosis is often difficult to treat, but it may respond to topical steroids and chemical peeling.Tretinoin has been used to enhance the efficacy of hydroquinone. In a large-scale, double-blind, placebo-controlled study, 0.05% tretinoin caused a decrease in melanin content at 6 months.
Mechanism of action: Hydroquinone produces reversible lightening of the skin by interfering with melanin production by the melanocytes. It works by decreasing the production and increasing the breakdown of melanosomes (melanin pigment granules) in the skin's pigment cells (melanocytes). It does this by inhibiting the activity of tyrosinase, the enzyme needed to make melanin.Specifically, inhibition of the enzymatic conversion of tyrosine to DOPA (dihydroxyphenylalanine) results in the desired chemical reduction of pigment. Ultimately, this causes a decrease in the number of melanocytes and decreased transfer of melanin leading to lighter skin.
The 2% hydroquinone is readily available over the counter in various cosmetic preparations. Evidence of improvement with hydroquinone (monotherapy) is usually observed at 4-6 weeks, with improvement appearing to plateau at approximately 4 months. For better efficacy, hydroquinone is compounded into various mixtures for the treatment of hyperpigmentation. The original Kligman formula involves compounding 5% hydroquinone with 0.1% retinoic acid and 0.1% dexamethasone in a hydrophilic ointment base. Tri-Luma is a popular combination skin-lightening agent that contains 0.01% fluocinolone, 4% hydroquinone, and 0.05% tretinoin in a cream formulation. Despite the remarkable overall safety of hydroquinone, bear in mind the potential adverse effects. Contact dermatitis occurs in a small number of patients and responds promptly to topical steroids. An uncommon, yet important, adverse effect of hydroquinone is exogenous ochronosis. This disorder is characterized by progressive sooty darkening of the skin area exposed to hydroquinone. Histologically, degeneration of collagen and elastic fibers occurs. This degeneration is followed by the appearance of characteristic ochronotic deposits consisting of crescent-shaped, ochre-colored fibers in the dermis. Exogenous ochronosis has generally been observed in black patients who have used high concentrations of hydroquinone for many years. Cases occurring after the use of 2% hydroquinone have also been reported, but assays of some of these products found that they actually contained much higher concentrations. An exogenous ochronosis due to hydroquinone has been reported from South Africa. For this reason, the general recommendation is that hydroquinone should be discontinued if no improvement occurs within 4-6 months. Hydroquinone-induced ochronosis is often difficult to treat, but it may respond to topical steroids and chemical peeling.Tretinoin has been used to enhance the efficacy of hydroquinone. In a large-scale, double-blind, placebo-controlled study, 0.05% tretinoin caused a decrease in melanin content at 6 months.
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