The small, round scar often found on the upper arm is frequently misidentified as a childhood injury or skin condition, but it is actually the result of the Bacillus Calmette-Guérin (BCG) vaccine, used to protect against tuberculosis (TB). Unlike modern intradermal injections, the BCG vaccine utilizes a weakened strain of Mycobacterium bovis, which triggers a deliberate, localized immune response. This process often involves the formation of a small blister or ulcer at the injection site that heals into a permanent, sunken scar. This mark is a biological record of the
The BCG Mark: Decoding the Science and Stigma of the World’s Most Common Scar
