https://www.scientificamerican.com/article/health-officials-claim-breakthrough-on-vaping-illness-culprit/

Health officials have identified a possible culprit behind the spate of vaping-related illnesses that have sickened thousands: vitamin E acetate.

The chemical—used as an additive or thickening agent in some vaping products—turned up in every sample of lung fluid collected from 29 patients with vaping-related illness, the Centers for Disease Control and Prevention reported Friday. While vitamin E acetate is used in supplements and skin creams and does not seem to cause harm when swallowed or used topically, previous research suggests that inhaling vitamin E acetate might impair people’s lung function.