Hydroquinone is a skin-lightening agent that bleaches your skin by decreasing the number of melanocytes present. It is worth noting that Melanocytes make melanin, which is the pigment in skin that gives it a brown color. Hydroquinone is typically used to lighten areas of darkened skin such as freckles, age spots, chloasma, and melisma caused by pregnancy, birth control pills, hormone medicine, or injury to the skin. By controlling melanocytes, your skin will become more evenly toned over time. It takes about four weeks on average for the ingredient to take effect. In fact, it may take several months of consistent use before you see full results. Although hydroquinone is generally well-tolerated, there are a few exceptions. If you have dry or sensitive skin, you may find that hydroquinone causes further dryness or irritation. And if you have a medium-to-dark skin tone, talk with your dermatologist before use, because Hydroquinone may actually worsen hyperpigmentation in darker skin tones.