Pure BG is explosive. I wouldn’t ever recommend putting a potentially explosive gas inside your body.
The reason we can inhale the gas is that we mix it with enough air that the % of hydrogen falls under the lower explosive limit in air (any mixture containing LESS than 4% hydrogen is non-explosive)…
The mixture is not toxic (exceedingly healthful in fact) but is explosive and is easily ignited by static electricity.
Putting the pure BG, (67% hydrogen, 33% oxygen) into the ears or rectum is just asking to really mess up or KILL a person.