What it is
Hydroquinone is a white crystalline solid.
What it does
Hydroquinone is used to lighten hyperpigmentation, like melasma, dark spots, age spots and freckles. It works by inhibiting melanin production.
Hydroquinone can cause sun sensitivity and should therefore always be used with a sunscreen.
It can cause a condition called exogenous ochronosis (it makes areas of their skin become darker).
In addition, it can also cause irritations in people with sensitive skin.
Allergies are rare, but can occur.
When exposed to sunlight or hair, hydroquinone oxidizes and becomes brown. Therefore, products containing this ingredient should be packaged in non-transparent containers.
(Sources: Journal of Drugs in Dermatology, March 2010 and Journal of the American Academy of Dermatology, November 2007)
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