Seeing a blue or blue-grayish spot on your baby's skin might raise a red flag, especially if the mark doesn't seem to go away. But these bruise-like marks actually aren't bruises at all — they're birthmarks called congenital dermal melanocytosis (formerly known as Mongolian spots). And — phew! — they're usually nothing to worry about.
What does a blue birthmark on baby's skin mean?
Congenital dermal melanocytosis spots are birthmarks that often appear around a baby's lower back, buttocks or shoulders. They're sometimes mistaken for bruises thanks to their blue-gray color, round and irregular shape, and flat texture. But unlike a bruise, they don't hurt at all and don't change color or shape quickly the way bruises often do. Some of these blue spots are tiny, while others can be 3 inches wide or more.[1]
These marks are much more likely to occur in babies of African, Asian, Indian and Mediterranean descent. But babies with light skin can sometimes develop congenital dermal melanocytosis, too.
Most of the time, congenital dermal melanocytosis is harmless and doesn't raise the risk for skin cancer. But the spots are tied to a slightly greater chance for certain underlying metabolic conditions.
Where do congenital dermal melanocytosis blue spots usually occur?
They're most common around the lumbosacral area — your baby's lower back, buttocks or shoulders. They don't usually show up on the head or face.
What causes congenital dermal melanocytosis?
Chalk it up to simple variations in skin pigment. Congenital dermal melanocytosis occurs when skin pigment cells called melanocytes cluster together in the deeper layers of your baby's skin. These spots appear gray, grayish-blue or grayish black because these colors have shorter wavelengths and are reflected to the skin's surface.
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Do blue birthmarks disappear?
Congenital dermal melanocytosis tends to be short-lived, usually fading away by the time your little one reaches her fourth birthday.[2] Occasionally, they can stick around longer, even into adulthood. When that happens, laser treatments can help get rid of a spot if your child is bothered by it.
Sometimes congenital dermal melanocytosis can be confused with bruising, especially if it shows up in atypical places. You can distinguish a blue birthmark from a bruise because it won't feel tender, does not change color or evolve with time, and may take several months to disappear.
When to speak to your baby’s pediatrician about congenital dermal melanocytosis
If the doctor doesn't notice your baby's blue birthmark during a routine well visit, point it out. While congenital dermal melanocytosis is usually harmless, these blue spots can in rare cases be tied to underlying conditions including neurocristopathies (a family of congenital disorders) and metabolic disorders. The pediatrician can keep an eye on the spot and assess your baby's risk for developing any associated conditions.
In all? These blue birthmarks can be alarming the first time you notice one. But they're rarely cause for concern, and will usually be gone by the time your child turns 2.
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