These flat, bluish-gray or brown patches are generally found on the back or buttocks and have an irregular border. They're common in babies with dark skin and can vary from freckle-size to quite large. Most fade over the course of a few years.
Since they can be mistaken for a bruise, have your doctor make a note of Mongolian spots in your child's health records in case there's ever a question about how it got there.
There's no need to do anything about these harmless marks because they eventually disappear and are usually not a significant cosmetic problem, says Dr. Rabinowitz.
Originally published in the November 2011 issue of Parents magazine.
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