It's most likely one of the following 4
`Hydroquinone is a commonly used and effective as a skin whitening cream.[5] It works by decreasing melanin production.[5] Side effects may rarely include exogenous ochronosis.[5] The European Union banned it from cosmetics in 2000.[5]
Tretinoin, also known as all-trans retinoic acid, may be used to whiten specific areas.[3] It may be used in combination with steroids and hydroquinone.[3] Side effects may include redness and sun sensitivity.[3] Use in pregnancy may harm the baby.[3]
How alpha hydroxy acid (AHA) works is unclear.[3] Side effects may include sun sensitivity, skin redness, thickening, or itching.[3] Low concentrations may be used in cosmetics.[3]
Kojic acid has been found to be useful in a number of studies.[3] Side effects however include redness, and eczema.[3] It is allowed to be used in cosmetics.[3] `
