I've been using e-cigs for a few months now off and on, and I noticed I get mild to fairly severe stomach cramping at times. I thought it may have been the nicotine, but found the non-nicotine blends did the same. I've only used the Propylene Glycol types, not the Glycerine. Wondering if anyone has any advice for a Glycerine based brand (I'm to lazy to fill them myself)