Some old beliefs tied birthmarks to past lives, as signs of how someone died previously (e.g., a birthmark on your back means you may have been stabbed in a past life, and a mark on the neck means there was decapitation in a past life). Others saw certain marks as karmic imprints, carrying emotional or physical baggage from before.
This idea is more common in spiritual or Buddhist-adjacent circles, and isn't mainstream, but it echoes beliefs found in other parts of Asia too.
Certain locations (like the face or forehead) were once thought to be unlucky or suggest bad karma. For example, a birthmark between the eyebrows might be seen as a spiritual “third eye”, or alternatively as something to watch out for, depending on who you ask.
Some people believe deceased relatives may leave a mark on a child being reborn. A birthmark might be interpreted as a sign that the soul has returned - particularly if it resembles a distinguishing feature the person had.
Pigmented birthmarks (like café-au-lait spots or moles) are due to extra pigment cells.
Vascular birthmarks (like hemangiomas) are from irregular blood vessel growth.
Most are harmless, some fade with age, and a few may need monitoring by a doctor, but none have magical or mystical origins.
To repeat: Birthmarks are biological, not mystical. They don’t signal bad luck, past-life trauma, or hidden supernatural abilities. They’re simply part of human variation, not a symbol of something deeper.