This product contains propylene glycol, which is also called "anti-freeze". There has not been enough human studies that document whether long-term use of this chemical in either of its forms, or any of its associated products can cause cancer, or other health-related problems. It is strange that 30 years ago propylene glycol was considered toxic and now the FDA does'nt think so. It seems that politics and not science is at work here. read full review »