I don't know, alot of people are using the electric pens on the big thread about it and most don't seem to report any problems. I have however found out after a weekly session with a pen i would have a big clump of hair in my hand afterwards that seemed to have been pulled out by the pen. So i stopped using the pen and just switched to a 1.5mm dermaroller instead, it doesn't wound as effectively but i don't have any hair getting pulled out using the roller. I didn't want to take the risk that those pulled out hairs wouldn't grow back.
