Hydroquinone belongs to a kind of whitening agent, if used for a long time up to 6 months, it may cause white spots to appear and achieve the opposite effect from the treatment, so the drug should be used properly under the guidance of a doctor. By affecting melanocyte production and reducing melanin deposition, hydroquinone can effectively treat pigmented skin diseases, such as freckles, melasma and other skin problems. In general, it is recommended to stop using hydroquinone for 6 months and visit a hospital for review. If used for more than 6 months and improperly used for a long time, hydroquinone may have a strong corrosive effect on skin and mucous membrane, or excessive pigment inhibition, appearing skin white spots, triggering skin inflammation problems, and in serious cases, dizziness, headache, nausea, vomiting and other manifestations may occur. In addition, because each person’s constitution is different, the adverse effects of using hydroquinone products are also different, but it is usually recommended not to use hydroquinone products for a long time, and to stop using them when the skin color of the applied area is the same as the normal skin color, so as not to lead to serious uneven skin color and white spots. When using hydroquinone products, you should pay attention to the application technique, only apply to the location of pigmentation spots, not to the healthy skin to avoid excessive suppression of pigmentation leading to uneven skin color and the problem of white spots. During the use period, if you go out in the daytime, you should do a good job of sun protection, not only apply sunscreen, but also use sunscreen caps and umbrellas at the same time.