I was severely burned by Bodytite which gave me a huge, festering blister. What caused this?

I think that any technology in which thermal energy is used to help create the result will have a risk for burns.  I will say that thinner skin and less fat individuals are probably at greater risk.

Because it is bipolar there is not a grounding pad.  The surface of the skin needs to have the ultrasound jelly applied.  I have had instance where I created a streak because I did not have enough ultrasound jelly.  these have all resolved.  Moist, clean wound healing is best for treating this area.