The causes of skin oxidation and dullness are sebum oxidation, water loss, ultraviolet radiation and other systemic diseases. 1. Sebum oxidation: Normal skin will secrete oil to maintain its own oil balance, to maintain sufficient moisture in the skin, the oil secreted is yellowish, and sebum and dust in the air and other contact, not timely cleanup will show a dull state. Improper cleaning often leads to acne, folliculitis and other conditions, aggravating the dullness. 2. Moisture loss: the skin can secrete a certain amount of oil, after cleaning the skin, if you do not replenish the water in time, the skin loss of moisture, will promote the sebaceous glands secretion of sebum to protect the skin, will be further oxidized, resulting in dullness. 3. Ultraviolet radiation: when ultraviolet radiation on the skin, the body’s melanin quickly change, there will be blackened, dull phenomenon. There are many other causes of skin oxidization and dullness, it is recommended to do a good job of daily sun protection, light diet, and replenish the water needed by the skin. 4. Other systemic diseases: other systemic diseases can also cause oxidation and dullness of the skin, such as blood system diseases, liver and gallbladder system diseases. If you have oxidized and dull skin, you need to go to a regular medical institution for medical treatment, exclude pathological factors, and then adjust your living habits and skin care in order to improve your symptoms.