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What causes birthmarks? Doctors have been stumped by their origins for years

What are birthmarks? And how do we get them?
What are birthmarks? And how do we get them? 02:34

Birthmarks are often harmless, but their origins have puzzled doctors for years.

More than 10% of babies are born with some kind of birthmark. Some fade over time, while others stay for life.

"Some types of birthmarks that we see have to do with how the skin cells migrate in the skin during development as well. It depends on the birthmark," said Dr. David Pearson, a dermatologist with M Health Fairview. "So it is forming in utero, in the womb, but not necessarily because of external events. So, you know, maternal diet and things like that probably don't play a major role most of the time."

Pearson says birthmarks can be caused by extra blood vessels which often show up as red. Extra pigment cells usually show up darker.

"Some types of birthmarks we call 'café au lait macules,' and those are kind of like light tan spots that we see like coffee" he said. "We see those in a lot of the population."

Pearson also says that genetics can play a role, but in general birthmarks aren't inherited.

"Café au lait macules, the coffee and milk types of spots, those people don't grow out of," he said.

If a birthmark affects self-esteem, there are treatment options like topical meds, laser therapy or surgery. Pearson also says that most birthmarks don't carry an increased risk of associated skin cancers.

Moles that develop after birth aren't birthmarks, neither are freckles. Anyone concerned about their skin should consult a doctor.

"We can step in and say, 'Yeah, this is what it is. Don't worry about it,' you know. Or maybe we keep a little bit of an eye on it, but yeah, we see a lot of birthmarks, very common," he said.

If you do notice changes to a birthmark, contact your healthcare provider.

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