Many girls are keen on skin whitening, even their buttocks. When we take a bath, we will find that there is no sunshine in their buttocks all the year round, but they feel rather dark, even dark from a distance. But why is it so dark where the sun can’t even touch? < / P > < p > black marks on the buttocks can occur in both adults and children, so you don’t have to worry about whether black marks on the buttocks will be a disease when you grow up. < / P > < p > the skin color of our buttocks and other parts of the body is mainly affected by melanin, and the density of black cells in different parts is different, so the degree of black and white is different. The area with the highest density of black cells is generally the genital area, so buttock black is associated with the melanin level of the body. < / P > < p > if there are two black spots on the buttocks of newborn babies, the main source is “Mongolian spot”, which is a kind of birthmark. This kind of green black birthmark area size is not fixed, but also may be distributed in the back, waist and other places, just happen to appear in the buttock, it will appear that the buttock black. < / P > < p > this kind of birthmark will not be malignant or cause physical injury, and some birthmarks will disappear with the growth and development of the child, so there is no need to worry too much. < / P > < p > if not only the buttocks are black, but also the skin surfaces of the face, thighs and other parts are black, it is likely that you have a high level of melanin and are naturally black, or that long-term exposure to ultraviolet light causes melanin accumulation. < / P > < p > students or office workers and other sedentary people are also prone to black buttocks. The buttock itself has too much adipose tissue, so the blood circulation is weak. If you sit for a long time, the blood circulation of the buttock will be blocked, the metabolism will slow down, and the melanin will be easy to accumulate. < / P > < p > if you wear tight pants for a long time, when you walk and run, your buttocks will rub with your pants more frequently, and the cuticle on your buttocks will thicken, causing the skin surface to become “black”. < / P > < p > the two black marks on the buttocks of obese people are usually more obvious than ordinary people, because obese people are more likely to have orange peel lines, local skin stratum corneum thickening and pigmentation. < / P > < p > for those who are sedentary for a long time, our doctors usually recommend that they get up every 45-60 minutes to remind them at their desks. < / P > < p > vitamin A ointment and skin care products containing fruit acid can help us exfoliate, but as a doctor, we need to remind you not to use drugs for external treatment without authorization. After pregnancy, do not let the wife do these five kinds of housework, the husband should be responsible for it, otherwise it is easy to hurt the fetus!