Safe For Consumption Compounds Can Still Be Lung Irritants | Ecig Advanced News. Most everything you can think of taken in excess will hurt or kill you. Vaping is not 100% safe. People who had never before had an allergic reaction to something earlier in their find that they have become hyper sensitive to it. The flavorings used in e-liquid could trigger an allergic reaction. Propylene Glycol [PG] can cause irritation to a small group at vaping levels. Others would have to be exposed to enormous amounts.