Hydroquinone produces reversible depigmentation of the skin by suppression of melanocyte metabolic processes , in particular the inhibition of the enzymatic oxidation of tyrosine to DOPA (3, 4 – dihydroxyphenylalanine ) ; sun exposure reverses this effect and will cause repigmentation.

Hydroquinone is used for the gradual bleaching of hyperpigmented skin conditions such as chloasma , melasma , freckles , senile lentigines and other unwanted areas of melanin hyperpigmentation.

Dermatitis ; Dryness ; Erythema; Stinging , Inflammatory reaction ; Sensitization ; Irritation

Hypersensitivity to hydroquinone or any component of the formulation ; Sunburn ; Depilatory usage

Hydroquinone should not be used to bleach eyelashes or eyebrows and contact with the eyes should be avoided as it may produce staining and corneal opacities . High concentrations or prolonged use may produce hyperpigmentation especially on areas of skin exposed to sunlight . Limit application to area no larger than face and neck or hands and arms.

Concurrent use with photosensitizing medications such as fluoroquinolones , phenothiazines , sulfonamides , tetracyclines , and thiazide diuretics is not recommended because of the possibility of augmented phototoxicity . Concurrent use with alcohol containing topical products , or those with strong drying effects , such as astringents , topical spices or lime , medicated soaps or shampoos , permanent wave solutions and electrolysis , hair depilatories or waxes , is recommended with caution because of the possibility of increased irritation.

Topical , applied to the skin of affected areas , twice daily , morning and evening at least 8 hours apart .

• USP DI, 2004
• Up To Date, Vol. 13.1 (2005)
• Martindale, The Complete Drug Reference, 33 rd edition 2002