Hydroquinone is a chemical compound that's commonly used in skincare and cosmetic products for its skin-lightening properties. It works to reduce the production of melanin, the pigment responsible for the color of skin, hair and eyes. Hydroquinone is often used to treat various skin conditions like melasma, age spots and post-inflammatory hyperpigmentation. Hydroquinone can be found in over-the-counter products as well as prescription-strength formulas, with various concentrations depending on the severity of the pigmentation concern. But, it should be used with caution and under the guidance of a healthcare professional because of potential side effects and concerns about its long-term safety, which have led to restrictions on its use in some countries.