Nevus simplex is the single most common vascular birthmark in newborns, appearing as a flat, pink-to-red patch on the skin and showing up in roughly 44% of all neonates.1PubMed Central. Persistent salmon patch on the forehead and glabellum in a chinese adult You may know it by its folk names: “stork bite” when it sits on the nape of the neck, “angel kiss” when it lands between the eyebrows or on the eyelids. Despite its prevalence and its dramatic-sounding medical label, it is overwhelmingly benign. Most facial lesions fade on their own in early childhood, though a subset, particularly those on the back of the neck, can stick around for life.
Where It Shows Up
Nevus simplex has a strong preference for specific body sites, and nearly all of them cluster along the midline. The most common locations are the glabella (the flat area between the eyebrows), the upper eyelids, and the nape of the neck.2PubMed. Nevus simplex: a reconsideration of nomenclature, sites of involvement, and disease associations Beyond those classic spots, patches can also appear on the forehead, nose, upper lip, scalp, and occasionally the lower back.3DermNet. Naevus simplex
A study of patients with more extensive nevus simplex found involvement at multiple sites simultaneously. Among those with widespread marks, the glabella was affected in about 78% of cases, the nose in roughly 67%, and the scalp (including the crown, back of the head, and sides) in a similar proportion. The nape and eyelids each appeared in over half, and lumbosacral skin was involved in about 56%.4PubMed. Nevus simplex: a reconsideration of nomenclature, sites of involvement, and disease associations The pattern matters because it helps clinicians distinguish nevus simplex from other vascular birthmarks. Port-wine stains, for instance, can appear anywhere on the body and tend to respect the midline on one side of the face, while nevus simplex almost always straddles the midline or sits squarely on it.
What Causes It
The pink color comes from dilated capillaries sitting close to the skin’s surface. During embryonic development, the cells that eventually form the skin’s nervous system migrate and fuse along the midline. In nevus simplex, that maturation process runs a little behind schedule, and the result is that the tiny blood vessels in the affected skin stay wider than they would otherwise be. Reduced regulation by the autonomic nerves that normally control blood vessel tone may also play a role.5DermNet. Naevus simplex – Section: What causes naevus simplex?
This is not a structural defect in the blood vessels themselves, which is one reason the marks are so prone to fading. The capillaries are normal vessels that happen to be a bit too relaxed. As the nervous system matures postnatally and gains better control over vascular tone, many of these patches quietly lose their extra blood flow and become invisible. That’s a very different situation from a port-wine stain, where the vessel walls themselves are abnormal due to a somatic genetic mutation.
The Fading Timeline
For most body sites, the news is reassuring. Nevus simplex on the face fades and disappears within the first one to two years of life.6DermNet. Naevus simplex – Section: What is the treatment and outcome for naevus simplex? Marks on the glabella, eyelids, nose, and upper lip are rarely detectable after age six.7PubMed Central. Persistent salmon patch on the forehead and glabellum in a chinese adult Parents often notice the patch getting temporarily brighter when the baby cries, strains, or gets warm, because those situations increase blood flow through the already dilated capillaries. That intensification is entirely normal and does not mean the birthmark is growing or worsening.
The nape of the neck is the major exception. A “stork bite” on the back of the neck fades more slowly and less completely than facial lesions, and it has roughly a 50% chance of persisting indefinitely.8DermNet. Naevus simplex – Section: What is the treatment and outcome for naevus simplex? Because the nape is usually covered by hair, many adults who carry one through life never realize it’s there. If you’ve ever noticed a pink patch on the back of someone’s neck when their hair is pulled up, there’s a good chance you were looking at a lifelong nevus simplex.
When It Persists Into Adulthood
While nape persistence is common and unremarkable, facial persistence is uncommon enough to warrant at least a brief note. A case report documented a 33-year-old woman with a salmon patch still visible on her forehead and glabella. Workup confirmed that the persistent facial mark was benign and not associated with any neurocutaneous syndrome or underlying vascular abnormality.9PubMed Central. Persistent salmon patch on the forehead and glabellum in a chinese adult In practical terms, a salmon patch that has not disappeared by middle childhood is unlikely to fade further, but it is also unlikely to signal anything worrisome. The mark can still become more visible with flushing, heat, or emotional stress, which sometimes leads adults who were unaware of the birthmark to think they have developed a new skin condition.
If a persistent facial lesion bothers someone cosmetically, the standard intervention is pulsed dye laser therapy, the same technology used for port-wine stains. This laser targets hemoglobin in the dilated vessels and causes them to shrink. The evidence base for treating nevus simplex specifically is thinner than for port-wine stains, but pulsed dye laser is recognized as the treatment of choice for capillary malformations in general.10Presse Médicale. Capillary malformations updates on aetiopathogenesis, diagnosis, and management Most dermatologists would advise watchful waiting in infancy and only consider laser treatment if the mark persists well beyond the expected fading window and causes distress.
Telling Nevus Simplex Apart From Other Vascular Birthmarks
The practical importance of getting this diagnosis right is hard to overstate. A nevus simplex needs no treatment, no imaging, and no follow-up visits in the vast majority of cases. A port-wine stain, by contrast, may darken and thicken over time and can in certain locations be associated with underlying structural abnormalities, including Sturge-Weber syndrome when it involves the upper face. Confusing the two can lead to unnecessary anxiety on one hand or missed evaluation on the other.
More widespread nevus simplex can look similar to a port-wine stain, and distinguishing them is not always straightforward in the first few weeks of life.11PubMed. Nevus simplex: a reconsideration of nomenclature, sites of involvement, and disease associations A clinical classification system has been proposed that organizes capillary vascular stains into seven major patterns, including nevus simplex, port-wine stain, reticulated capillary malformation, and several others, each with different clinical trajectories.12PubMed Central. Vascular Stains: Proposal for a Clinical Classification to Improve Diagnosis and Management In practice, here are the features that point toward nevus simplex rather than a port-wine stain:
- Location: Nevus simplex clusters at midline sites (glabella, nape, eyelids). Port-wine stains can occur anywhere and tend to be unilateral.
- Color: Nevus simplex is typically a soft salmon-pink that blanches easily with pressure. Port-wine stains are often darker red or purple and may blanch less readily.
- Borders: Nevus simplex usually has indistinct, feathered edges that blend into surrounding skin. Port-wine stains tend to have sharper, more geographic borders.
- Behavior over time: Nevus simplex fades; port-wine stains generally do not, and they may darken.
Infantile hemangiomas are a different category entirely. Unlike nevus simplex and port-wine stains, which are flat, hemangiomas are proliferating tumors of blood vessel cells. They typically are not present at birth (or appear as a faint precursor) and then grow rapidly during the first months of life before slowly involuting. The clinical course is so different that confusion between a hemangioma and a nevus simplex usually resolves itself within weeks.
When Nevus Simplex Needs a Closer Look
The vast majority of nevus simplex patches require nothing more than reassurance. But there are specific situations where the presence of a salmon patch should prompt further evaluation.
The most clinically significant scenario involves the lumbosacral area. Sacral lesions are not uncommon in nevus simplex, especially the more extensive variant sometimes called “nevus simplex complex.” On their own, these lower-back patches are still benign. However, when a lumbosacral salmon patch appears alongside a second midline anomaly in the same region, such as a deep sacral dimple, a tuft of hair, or a skin tag, further evaluation for underlying spinal dysraphism should be considered.13Journal of the Dermatology Nurses’ Association. Nevus Simplex Spinal dysraphism refers to a spectrum of developmental abnormalities where the spinal column does not close completely, and early detection matters because some forms require surgical intervention.
This does not mean every baby with a pink patch on the lower back needs an MRI. A solitary nevus simplex in a typical midline location with no other skin findings is managed with observation. The red flag is the combination: vascular mark plus another cutaneous anomaly in the same area. Pediatricians are generally trained to look for this pattern during routine newborn exams.
The Naming Problem
One reason nevus simplex can be confusing for parents doing their own research is that the terminology is a mess. “Salmon patch,” “stork bite,” “angel kiss,” “nevus flammeus neonatorum,” “Unna’s nevus” (for the nape variant), and “nevus simplex” itself all refer to the same entity or subsets of it, depending on who is writing and when. Some older dermatology textbooks grouped nevus simplex under the broader umbrella of “nevus flammeus,” which also includes port-wine stains, creating the misleading impression that the two are variants of one condition rather than biologically distinct entities.
The push in recent years has been to standardize terminology around “nevus simplex” as the preferred name for the benign, fading capillary dilation, and to reserve “port-wine stain” or “capillary malformation” for the persistent, sometimes syndromic lesions caused by somatic mutations. The distinction matters beyond semantics because it determines whether a family is told “this will almost certainly go away” or “this is permanent and we should evaluate for associated findings.” Using clear terminology from the outset helps avoid the unnecessary anxiety that comes from a parent Googling “nevus flammeus” and landing on pages about Sturge-Weber syndrome.
Parental Anxiety and What Doctors Can Do About It
Even when a birthmark is entirely harmless, seeing any kind of mark on a newborn’s skin can be unsettling. Neonatal skin conditions in general, even the clearly benign ones, tend to provoke outsized worry because new parents have little frame of reference for what is normal. Clinical presentations that look dramatic to a layperson can cause significant anxiety, and that anxiety is worth addressing directly rather than dismissing.14PubMed Central. Newborn Skin: Common Skin Problems
For nevus simplex specifically, the most helpful thing a clinician can do is explain three things clearly. First, how common the mark is. Telling a parent that nearly half of all newborns have some version of this birthmark is immediately normalizing. Second, what the expected timeline looks like: facial marks usually gone within a year or two, nape marks often staying indefinitely but hidden by hair. Third, the specific signs that would warrant a return visit, namely a mark that is darkening rather than fading, growing, developing a raised texture, or appearing alongside other skin abnormalities in the lumbosacral region. Providing this framework upfront spares parents from anxious monitoring of a normal fading process and gives them clear criteria for when concern is actually warranted.
Maternal and Neonatal Factors
Researchers have examined whether certain maternal or neonatal characteristics make nevus simplex more or less likely. Studies have looked at factors including the baby’s sex, gestational age, and birth weight, as well as the mother’s age, number of previous pregnancies, and mode of delivery.15PubMed. Cutaneous lesions and disorders in healthy neonates and their relationships with maternal-neonatal factors: a cross-sectional study The relationships examined in these cross-sectional studies have generally not produced strong, consistent predictors. Nevus simplex appears across all demographic groups, regardless of ethnicity, sex, or delivery method. This aligns with the understanding that the mark reflects a minor variation in the timing of embryonic development rather than a response to any particular environmental exposure or obstetric event.
That said, prevalence figures vary somewhat by population studied, which likely reflects differences in skin pigmentation and clinical detection rather than true differences in occurrence. In darker skin, a faint salmon patch may be much harder to see, leading to lower reported rates in certain populations. The underlying biology appears to be the same regardless of skin tone.
Dermoscopy and Evolving Diagnostic Tools
In most cases, nevus simplex is diagnosed on clinical appearance alone: a flat, salmon-pink, midline patch in a newborn that blanches with pressure. No biopsy is needed, and no blood tests are useful. When there is diagnostic uncertainty, particularly in differentiating a fading nevus simplex from an early port-wine stain, dermoscopy can help. Under a dermatoscope, nevus simplex tends to show a diffuse, homogeneous red-pink background without the more structured vascular patterns seen in port-wine stains.
For the rare cases that remain ambiguous after clinical and dermoscopic evaluation, the passage of time is the most reliable diagnostic tool. A mark that is clearly lighter at three months than it was at birth is behaving like a nevus simplex. A mark that holds steady in color or deepens is more concerning for a capillary malformation and may warrant referral to a pediatric dermatologist or vascular anomalies specialist. The classification framework that divides capillary vascular stains into distinct clinical patterns was designed precisely for these borderline cases, giving clinicians a shared language for the features that separate one type from another.16PubMed Central. Vascular Stains: Proposal for a Clinical Classification to Improve Diagnosis and Management
Genetic testing plays essentially no role in diagnosing or managing standard nevus simplex. Unlike port-wine stains, which are increasingly understood as the result of somatic mutations in specific growth-signaling pathways, nevus simplex has not been linked to a particular gene variant. The broader family of capillary malformations and overgrowth syndromes does involve well-characterized mutations in pathways like PIK3CA, but these conditions produce clinical pictures far more complex than a simple salmon patch.17Current Opinion in Pediatrics. Update on classification and diagnosis of vascular malformations If a clinician suspects one of these syndromic conditions, the investigation would be driven by the associated findings (overgrowth, limb asymmetry, structural anomalies), not by the vascular stain alone.