If you grew up in Asia, Africa, Latin America, or parts of Eastern Europe, there’s a good chance you have a small, round scar on your upper arm. Many people notice it later in life and wonder where it came from. Some feel embarrassed by it. Others invent explanations because no one ever explained the truth.

That little scar has sparked decades of confusion. Below are five of the most common misconceptions about the round scar on the arm—and the real facts behind it.

Misconception 1: “It’s a skin disease or a childhood injury”

One of the most widespread beliefs is that the scar is the result of a skin condition, an infection, or an injury from childhood. Some people even assume it came from a burn or an untreated wound.

The truth: