Many designs I have seen for wearable sensing and actuation employ non-insulated conductors near or on the skin of the wearer.
This puts people at risk from the dangers of faults in the protections provided by the devices the wearable system is plugged into.
One way to mitigate this risk for USB powered devices is to use a galvanic isolator. The design of these is documented in Adafruit’s isolator:
For development situations it is better to employ an isolator already built into an insulated box such as this one:
or this one:
For final production situations it is better to incorporate the isolation into the device your are making itself to avoid inviting people to save money or time and bypass an external isolation box.