[femto]

> At least here in the EU they do

In that case it was a cheap USB supply, though there are other reports of similar. "Good" consumer power supply are designed to IEC standards, but to keep the cost down they are different standards to those used for wearable medical equipment. Medical equipment has to conform to IEC 60601, which governs things like electrical isolation and safe failure modes.

> i feel pretty safe

So be it. It is unlikely, but even a good power supply can fail in the face of a voltage surge on the mains. Absolutely don't wear it plugged in if there is any hint of a thunderstorm!