The sudden darkening of skin tone may be caused by a variety of reasons, such as ultraviolet radiation, irregular work and rest, excessive stress, certain diseases or uneven diet. To whiten back quickly, you can try the following methods： 1. **Strict sun protection**: Ultraviolet rays are one of the main causes of darkening skin tone. When going out, apply high-strength sunscreen, wear hats, sunglasses, and umbrellas, and avoid going out during the period when ultraviolet rays are strongest (10 a.m. to 4 p.m.). 2. **Adjust your work and rest**: Maintain adequate sleep and try to ensure 7-8 hours of high-quality sleep every night, which is conducive to body metabolism and skin self-repair, and is beneficial to improving skin tone. 3. **Relieve stress**: Long-term high stress status can affect endocrine, which in turn affects skin tone. Stress can be relieved through meditation, yoga, deep breathing, listening to music, etc. 4. **Dietary conditioning**: Eat foods rich in vitamin C, vitamin E, glutathione and other whitening ingredients, such as oranges, lemons, strawberries, kiwifruit, nuts, broccoli, spinach, etc. Reduce the intake of foods high in sugar, fat, and salt. 5. **Skin cleansing**: Do a good job of cleaning the skin, choose gentle cleansing products, wash your face in the morning and evening to remove dirt and oil from the surface of the skin, but be careful not to over-clean, so as not to damage the skin barrier. 6. **Whitening skin care products**: Use skin care products that contain whitening ingredients such as tranexamic acid, niacinamide, arbutin, etc., such as whitening serums, face creams, etc., but the whitening effect takes a certain time to appear, and pay attention to whether the product is suitable for your skin type and avoid allergies. 7. **Regular exfoliation**: Moderate exfoliation can help remove aging keratinocytes accumulated on the surface of the skin, make the skin smoother and more delicate, and promote the absorption of whitening products. But exfoliation should not be too frequent, just 1-2 times a week. 8. **Moisturizing and moisturizing**: The skin will appear more translucent when it is well hydrated. Drink enough water every day and use skin care products such as moisturizing toners, lotions, and masks to keep your skin hydrated.