A red birthmark is a cluster of blood vessels that formed unusually in the skin, either before birth or in the first few weeks of life. These vascular birthmarks are extremely common, appearing in 20 to 30 percent of newborns, and most are completely harmless. The specific type of red birthmark determines whether it will fade on its own, stay the same, or change over time.
Red birthmarks fall into two broad categories: vascular tumors (the most common being hemangiomas) and vascular malformations (like port-wine stains and salmon patches). The distinction matters because tumors grow by producing extra cells and often shrink on their own, while malformations are structural irregularities in blood vessels that are present from birth and typically persist.
Salmon Patches: The Most Common Type
Salmon patches are flat, pale pink marks that appear on roughly one in three newborns. They go by different nicknames depending on location: “stork bites” on the back of the neck, “angel kisses” on the eyelids or forehead. The nape of the neck is the single most common spot, affecting about 38 percent of infants who have them, followed closely by the eyelids at 35 percent.
These marks are caused by dilated capillaries sitting close to the skin’s surface. Most salmon patches on the face fade within the first year or two of life. Those on the back of the neck tend to stick around longer, sometimes permanently, but they’re usually hidden by hair and rarely cause any issues.
Infantile Hemangiomas
Infantile hemangiomas are the most common benign tumors in infancy, showing up in 4 to 5 percent of full-term newborns. They’re rarely visible at birth. Instead, they typically appear in the first few weeks of life as a small red spot, then grow rapidly.
The growth follows a predictable pattern. The rapid proliferation phase runs from birth through roughly the first year, with the fastest growth happening between months one and five. After about 18 months, the hemangioma enters its shrinking phase. About 50 percent resolve completely by age 5, and around 70 percent are gone by age 7. Some continue improving through age 10 to 12. The skin left behind is often normal, though larger hemangiomas can leave behind loose or slightly discolored skin.
Most hemangiomas need no treatment at all. However, location matters. A hemangioma near the eye can interfere with vision development. One near the mouth can affect feeding. And in rare cases, hemangiomas in the airway can compromise breathing. These situations call for early intervention. An oral medication that slows blood vessel growth is now the standard treatment for problematic hemangiomas, and in clinical trials, 60 percent of infants treated for six months achieved complete or nearly complete resolution, compared to just 4 percent with a placebo. About 10 percent of successfully treated infants needed retreatment later for recurrence.
Port-Wine Stains
Port-wine stains are a different story entirely. Found in about 1 percent of newborns, these flat, pink-to-red marks are caused by malformed capillaries in the skin, not a tumor that will shrink. They’re present at birth, and unlike hemangiomas, they never go away on their own.
What makes port-wine stains worth understanding is that they change over time. In infancy and childhood, they typically appear as flat, light pink patches. Over the following decades, the blood vessels gradually widen. The color deepens from pink to red to purple. The skin can thicken and develop a bumpy, cobblestone-like texture. A review of over 400 patients found that roughly 65 percent had developed thickened or nodular skin by their fifties, with the average age of thickening around 37.
Laser treatment is the primary approach for port-wine stains and works best when started early, while the marks are still flat and light-colored. Studies on infants suggest that early, consistent treatment can inhibit progression and may reduce the risk of the color returning. The number of sessions varies widely, with some patients needing as few as two and others needing 20 to reach near-total clearance. Treating port-wine stains in their flat stage helps prevent the thickening and nodularity that develop over time if the marks are left alone.
What Causes Red Birthmarks
Red birthmarks are not caused by anything that happened during pregnancy. They result from random errors in how blood vessels develop in a small area of tissue. For hemangiomas, the trigger is still not fully understood, but the cells lining blood vessels proliferate abnormally, creating a dense tangle that appears red or bluish through the skin.
For port-wine stains, the genetic mechanism is more clearly mapped. A specific mutation in a gene called GNAQ causes endothelial cells (the cells lining blood vessels) to proliferate more than normal, producing an overgrowth of capillaries in the affected skin. This mutation is somatic and mosaic, meaning it occurs randomly in a small group of cells during fetal development. It’s not inherited from parents and can’t be passed on to children.
When a Red Birthmark Signals Something Broader
The vast majority of red birthmarks are isolated skin findings with no deeper significance. In a small number of cases, though, a port-wine stain in a specific location can be associated with a condition called Sturge-Weber syndrome, which involves blood vessel abnormalities not just in the skin but also in the brain and eyes.
Sturge-Weber syndrome has three hallmark features: a facial port-wine stain (typically on the forehead, temple, or eyelid, usually on one side), abnormal blood vessels on the surface of the brain, and elevated pressure in the eye that can lead to glaucoma. Not every facial port-wine stain means Sturge-Weber syndrome is present, but a port-wine stain in the upper part of the face, particularly involving the forehead and eyelid, is the pattern that prompts further evaluation. Screening typically involves eye exams and brain imaging to check for the other features.
Telling Red Birthmarks Apart
If you’re looking at a red mark on a baby or on yourself and trying to figure out what it is, a few key differences help distinguish the types:
- Salmon patches are flat, pale pink, present at birth, and most often found on the eyelids, forehead, or back of the neck. They fade when pressed and usually disappear in infancy.
- Infantile hemangiomas are rarely visible at birth but appear within the first few weeks. They grow quickly into raised, bright red bumps (sometimes called “strawberry marks”) and then slowly shrink over several years.
- Port-wine stains are flat, present at birth, and do not fade over time. They start pink and gradually deepen in color. They can appear anywhere on the body but are most clinically significant on the face.
A red birthmark on an adult that has been there since birth or early infancy is most likely either a port-wine stain or the residual mark of a hemangioma that has already gone through its growth and shrinking cycle. New red spots appearing in adulthood are not birthmarks and have different causes, such as cherry angiomas, which are small, benign growths of blood vessels that become increasingly common with age.