You may have noticed a distinct scar that some people carry on their upper left arm. It’s subtle but curious enough to spark questions: What causes this mark? Is there a hidden meaning or story behind it?
The Common Explanation
Most often, this scar is the result of a BCG vaccination (Bacillus Calmette-Guérin), a vaccine primarily used against tuberculosis (TB). The BCG vaccine is typically administered on the upper left arm in many countries. Unlike regular shots, it often leaves a small but permanent scar after healing.
Why the Scar?
The BCG vaccine contains a weakened strain of the bacteria that cause TB, which helps the body build immunity. The injection causes a localized reaction on the skin, leading to a small ulcer or sore that eventually heals but leaves behind a noticeable scar.
Is It Dangerous?
Absolutely not. The scar is a sign that the vaccine worked as intended. In many parts of the world, especially where TB is still a concern, this vaccination is a standard childhood immunization.
Other Possible Causes
While the BCG vaccine scar is the most common cause, similar scars can also come from other injections, minor surgeries, or skin conditions. But if you see this specific type of scar on the upper left arm, the BCG vaccination is the likely explanation.