A birthmark is a colored spot or patch on the skin that’s present at birth or appears within the first few weeks of life. Birthmarks are extremely common, and most are harmless. They fall into two broad categories based on what’s happening beneath the skin: vascular birthmarks, caused by blood vessels that didn’t form correctly during fetal development, and pigmented birthmarks, caused by clusters of the cells that give skin its color.
Vascular Birthmarks
Vascular birthmarks get their color from blood vessels. They tend to appear pink, red, or purple depending on how deep and dense the affected vessels are. The three most common types look and behave quite differently from one another.
Salmon patches are the most frequent vascular birthmark, showing up in roughly 36% of newborns. They’re flat, pink or red, and have soft, poorly defined edges. You’ll often hear them called “stork bites” when they appear on the back of the neck or “angel kisses” when they show up between the eyebrows or on the eyelids. Most salmon patches on the face fade within a year or two, though ones on the back of the neck are less likely to disappear completely and can persist into adulthood.
Hemangiomas are raised, bright red, and soft to the touch with well-defined borders. They most commonly appear on the face, scalp, chest, or back. Unlike other birthmarks, hemangiomas typically grow during the first several months of life before gradually shrinking on their own. They occur in about 1% of newborns.
Port-wine stains are flat patches of purple or dark red skin, often large, and usually on one side of the face or neck. They’re present in less than 1% of newborns. Unlike salmon patches, port-wine stains don’t fade with time. They actually tend to darken and thicken as a person ages. By the mid-forties, about two-thirds of people with port-wine stains develop soft tissue overgrowth and small nodules in the affected area, sometimes causing asymmetry or spontaneous bleeding.
Pigmented Birthmarks
Pigmented birthmarks form when pigment-producing cells cluster together in one area of the skin instead of spreading evenly. They range widely in color and size.
Mongolian spots (also called dermal melanocytosis) are bluish or bruised-looking patches, most often on the lower back or buttocks. They’re the single most common pigmented birthmark, appearing in roughly two-thirds of newborns in some populations. They typically fade during childhood.
Café-au-lait spots are flat, light tan patches, the color of coffee with milk. They’re found in about 30% of newborns. A single spot is usually nothing to think twice about. Multiple café-au-lait spots, however, can sometimes signal an underlying genetic condition called neurofibromatosis, so doctors pay attention to the number and size.
Congenital moles (congenital melanocytic nevi) are spots made of small clusters of colored skin cells. They appear in fewer than 2% of newborns. Most are small and benign, but large congenital moles, particularly those bigger than the size of a fist, carry an increased risk of developing melanoma over a person’s lifetime and are typically monitored closely.
How Birthmarks Form
Birthmarks develop during fetal growth, but they aren’t caused by anything a parent did or didn’t do during pregnancy. The process is biological and largely random.
For pigmented birthmarks, precursor cells that will eventually produce skin pigment migrate outward from the center of the developing embryo. This migration happens through a combination of cell division and random diffusion rather than any directed movement. When clusters of these cells end up concentrated in one spot instead of spreading evenly, the result is a visible mark on the skin.
Vascular birthmarks follow a similar principle with blood vessels. During fetal development, small blood vessels in certain areas form abnormally, either growing too densely (as in hemangiomas) or dilating wider than normal (as in port-wine stains). Researchers have found that the patterns of these birthmarks correspond to specific developmental zones in the embryo’s face and body rather than to the adult blood supply, which helps explain why certain types consistently appear in predictable locations.
Some birthmarks have a clear genetic fingerprint. Port-wine stains, for instance, are caused by a somatic mutation in a gene called GNAQ. “Somatic” means the mutation happens spontaneously in a subset of cells during development rather than being inherited from a parent. The proportion of mutated cells in the affected area correlates with severity: more mutated cells means a more pronounced birthmark.
When a Birthmark May Signal Something Else
The vast majority of birthmarks are purely cosmetic. But in a small number of cases, certain types can be associated with deeper medical conditions.
A port-wine stain on the forehead, temple, or eyelid, particularly one that covers only one side of the face, is the hallmark of Sturge-Weber syndrome. This rare condition involves abnormal blood vessels not just in the skin but also in the eyes and brain, and can lead to seizures, glaucoma, or developmental differences. Not every facial port-wine stain means Sturge-Weber, but the location prompts doctors to evaluate further.
Multiple café-au-lait spots, especially six or more above a certain size, are one of the diagnostic criteria for neurofibromatosis, a genetic condition that causes tumors to grow along nerves. Again, having one or two spots is common and typically meaningless on its own.
Large congenital moles deserve ongoing monitoring because of their elevated melanoma risk. Your dermatologist can help determine how often to check and whether any changes in color, shape, or texture warrant a closer look.
Treatment Options
Many birthmarks need no treatment at all. Salmon patches and Mongolian spots tend to fade on their own, and small pigmented marks are often left alone. Treatment is typically pursued when a birthmark causes physical symptoms, affects function (near the eye or mouth, for example), or when someone wants it addressed for cosmetic reasons.
For hemangiomas that are growing rapidly or located in sensitive areas, a blood pressure medication called propranolol has become a standard treatment. It works by narrowing the blood vessels within the hemangioma, softening it, reducing its color, and limiting further growth.
Laser therapy is the most common approach for port-wine stains and superficial vascular birthmarks. Short bursts of laser light target the blood vessels close to the skin’s surface, lightening the color and improving texture. Multiple sessions are usually needed, and the treatment works best when started early in life while the mark is still lighter and thinner. For port-wine stains, laser therapy can significantly lighten the appearance but rarely eliminates the mark entirely.
Surgical removal is reserved for cases where a birthmark is deep, affecting surrounding tissue, or carries a medical risk, such as large congenital moles. Some vascular malformations are treated with sclerotherapy, where a substance is injected into the abnormal vessel to close it off and stop blood flow through it.
For pigmented birthmarks that are purely cosmetic concerns, the decision to treat is personal. Many people live comfortably with their birthmarks and consider them a distinctive feature rather than something that needs correction.