The appearance of white stuff on the roots of the thighs of newborn babies may be fetal fat, or it may be due to diseases such as leucoderma and vitiligo. A white layer of greasy fat appears on the skin of a newborn baby, which can be distributed on all parts of the body, and is the fat that the fetus carries from the mother’s stomach when it is born. Fetal fat is the result of a pregnant woman taking in more nutrients during pregnancy, which speeds up the fetus’s metabolism, thus causing the fetus to secrete more fat. Fetal fat protects the newborn’s skin and maintains body temperature. Children with pityriasis alba may present with red patches on various parts of the body, which turn into white patches when the red patches subside and are accompanied by scales, etc. Vitiligo often appears on the face and neck, lumbosacral region and other parts of the body, patients often show localized appearances of varying numbers of white patches of different shapes and sizes. When the affected children feel uncomfortable, they should go to the hospital immediately.