Selects: Birthmarks: Probably Not the Mark of the Devil
Episode of Stuff You Should Know · June 20, 2026 · 50 min
Josh Clark and Chuck Bryant explain the types, causes, treatments, and folklore of birthmarks, plus a listener's list of band names from past episodes.
Summary
In this rerun of a February 2020 episode of Stuff You Should Know, hosts Josh Clark and Chuck Bryant discussed birthmarks. After banter about skin tags, warts and freckles, Clark noted that people have long been ostracized for birthmarks, historically as supposed signs of witchcraft or Satan, and still today because they look different.
The hosts divided birthmarks into vascular types (macular stains such as angel kisses, stork bites and salmon patches; port wine stains; and hemangiomas or strawberry marks) and pigmented types (café au lait spots, Mongolian spots, and moles). Clark explained that science largely does not know what causes birthmarks, though a gene locked in the on position has been linked to port wine stains through research on Sturge-Weber syndrome, and that six or more café au lait spots can indicate neurofibromatosis. Both warned that atypical moles are associated with melanoma, which Clark argued is more serious than many people think; Bryant mentioned a family member being treated for it.
On treatment, Clark described pulsed dye laser therapy for vascular birthmarks and groups such as the British Association of Skin Camouflage and Changing Faces. The hosts then surveyed folklore, including beliefs that maternal behavior during pregnancy caused birthmarks, the doctrine of signatures, past-life explanations such as a reported Syrian case, and the Russian nobility's supposed use of birthmarks to prove lineage. They closed with an appeal against teasing children with birthmarks and a listener mail segment listing band names coined on the show.
Chapters
- 0:05
Introduction and skin tags
Chuck introduces the 2020 rerun and the hosts trade stories about birthmarks, skin tags, and childhood warts.
- 6:01
Birthmark stigma
Josh describes how people with birthmarks have been ostracized historically and today.
- 8:09
Macular stains and port wine stains
The hosts explain vascular birthmarks, including angel kisses, stork bites, and port wine stains linked to Sturge-Weber syndrome.
- 14:25
Hemangiomas and why deep blood looks blue
The hosts discuss strawberry marks and debunk the myth that deoxygenated blood is blue.
- 19:14
Pigmented birthmarks and a coffee detour
Discussion of melanin, talking to children about skin color, and a tangent on coffee drinks, thermoses, and sushi.
- 25:19
Café au lait spots, Mongolian spots, and moles
The hosts cover café au lait spots and neurofibromatosis, Mongolian spots, mole types, and melanoma risk.
- 31:46
Beauty marks
The hosts discuss celebrity beauty marks and the lack of celebrities with visible birthmarks.
- 34:12
Treatment and skin camouflage
Josh explains pulsed dye laser treatment and groups that promote camouflage and acceptance of facial differences.
- 39:26
Superstitions and folklore
The hosts survey beliefs about birthmarks, from maternal impressions to past lives and Russian nobility.
- 44:29
Closing message and listener mail
The hosts urge kindness toward children with birthmarks and read a listener's list of band names from past episodes.
Key points
What was said, by whom, with the exact words. Timestamps jump to the moment.
- Josh Clark
Clark says dermatologists do not actually know what causes birthmarks in general.
“What causes birthmarks? They would say we actually don't know. The closest that they've come is with port wine stains from what I can tell”
- Josh Clark
Clark says about 6% of children born with port wine stains develop Sturge-Weber syndrome, a neurological condition.
“about 6% of kids who are born with the port wine stain birthmark develop something called Sturge-Weber syndrome, which is a neurological condition”
- Josh Clark
Clark explains that researchers traced port wine stains to a gene whose molecular switch is locked in the on position.
“They figured out that there's a gene where this molecular switch that's supposed to go on and off is locked in the on position”
- Josh Clark
Clark explains that deeper blood vessel clusters look blue because of how light penetrates and reflects, not because deoxygenated blood is blue.
“The reason it's blue is because the deeper it is, the less blue light is able to penetrate, so the less that can be absorbed”
- Chuck Bryant
Bryant says strawberry marks usually disappear by the time a child reaches double digits and are most common on Caucasian girls.
“they will disappear usually by the time a kid is like into double digits. If they're large, sometimes you might see a scar”
- Josh Clark
Clark advises that six or more café au lait spots, especially larger than a dime, warrant a doctor's visit to check for neurofibromatosis.
“if you have six or more of these kinds of cafe au lait birthmarks, especially if they're larger than like a dime in an older kid, you want to go to see a doctor”
- Josh Clark
Clark argues that atypical moles are linked to melanoma and that melanoma is far more dangerous than many people assume.
“No, melanoma can spread like lightning through your body, and it can be a real problem. It's a very serious thing to keep up with”
- Chuck Bryant
Bryant says a family member's melanoma, now being treated successfully, showed him how serious the disease is.
“The treatment is going really well, but it has definitely opened my eyes to the fact that it's no joke”
- Chuck Bryant
Bryant observes that cancers differ in public awareness, with breast cancer outpacing prostate cancer in marketing.
“prostate cancer has often lagged behind breast cancer. Like breast cancer does a bang-up job of marketing and press and PR and awareness”
- Josh Clark
Clark explains that pulsed dye lasers work because the birthmark absorbs a targeted wavelength that surrounding skin does not, converting light to heat.
“that light energy, is translated into heat energy in the birthmark, and there go the cells or the blood vessels that make up the cells”
- Chuck Bryant
Bryant says removal usually targets vascular birthmarks, while doctors generally do not treat pigmented ones.
“So if you are getting something removed, it's usually a vascular birthmark. Generally, they don't try and get rid of pigmented birthmarks”
- Josh Clark
Clark endorses Changing Faces' view that society, not people with facial differences, needs to adjust.
“Like, their face is different for any number of reasons. And it's really kind of on the rest of you to get over it”
- Josh Clark
Clark says that because birthmarks were unexplained, societies worldwide blamed them on something the mother did during pregnancy.
“all over the world, people, societies have said it's something the mom did while she was pregnant”
Linked moment · 43:03Skip to 43:03 using a listen link in the info box.
Josh ClarkClark recounts a reported Syrian case of a boy with a birthmark who described a past-life axe murder, while saying he doubts it happened.
“There's just no way that that happened, but I love reading about stuff like that”
- Josh Clark
Clark says Russian nobility from the 17th to 19th centuries proved their status by displaying birthmarks, which he finds plausible given possible heritability.
“From the 17th to the 19th centuries, if you were Russian nobility, you proved it by displaying your birthmark”
- Chuck Bryant
Bryant urges parents to teach children that classmates with visible birthmarks are no different and should not be teased.
“just explain to your kids if there's another kid in their class that has, you know, a pretty obvious birthmark, that they're just the same”
People
In the conversation
- Josh ClarkCo-host of Stuff You Should Know
- Chuck BryantCo-host of Stuff You Should Know
Discussed
- Anne BoleynQueen of England, second wife of Henry VIII, legendarily accused of witchcraft
- Marilyn MonroeAmerican actress known for her beauty mark
- Cindy CrawfordAmerican model known for her beauty mark
- Spiro AgnewU.S. vice president under Richard Nixon, frequently mocked by Mad Magazine
Topics
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From the publisher
It’s a pretty safe assumption that people have been born with birthmarks since humanity began, and between then and now we’ve come up with some wacky, even dangerous, explanations for them – even a few that survive still today. Learn all about them in this classic episode. See omnystudio.com/listener for privacy information.
Summary, chapters and key points were generated from the episode transcript on September 29, 2026. Quotes are checked word for word against the transcript.