Propylene Glycol Side Effects (Toxicity, Allergy, Vape) Do Vapes Have Sugar? The Truth About Sweeteners and Vaping Qu'est ce que le propylne glycol ? Rle en e cigarette Propylene Glycol BP EP The Vape Alchemist Researchers at the University of California, Riverside, found that heating propylene glycol, the main ingredient in most e cigarette liquids, can produce two toxic chemicals, methylglyoxal and acetaldehyde, which damage lung cells. Using