If you’re referring to the small round scar many people have on their upper arm, it is often the result of a childhood vaccination rather than an injury.
The most common historical cause is the Smallpox vaccine, which was administered using a special technique that frequently left a distinctive circular scar. Because smallpox was eradicated worldwide, routine smallpox vaccination stopped in most countries decades ago, but many older adults still have the scar.
In some countries, the Tuberculosis vaccine, known as BCG vaccine, can also leave a small round scar on the upper arm. The appearance varies by person and vaccination method.
Why does the scar form?
Unlike many modern injections, these vaccines often produced a local skin reaction:
- A small bump forms.
- The area may ulcerate or scab.
- It heals over several weeks.
- A permanent scar can remain.
Can you tell which vaccine caused it?
Not always. It depends on:
- Your age
- The country where you were vaccinated
- The scar’s size and appearance
- Historical vaccination practices in your region
Other possible causes
