I’ve recently studied the harm element a lot. Someone would be better smoking some tobacco than vaping, instead. Propylene glycol and vegetable glycerin are the two inhalants used but when used with vaping, the daily dose is 1,000 what an asthma inhaler user, which has the same ingredients, would take into the body.
PG is cytotoxic. The skin is an organ of elimination, hence the 1 in 10 problem of total body rash. It still is affecting internal cells even though a skin reaction is not manifested.
Also, with vaping, flavours are now added (for the first time ever). No-one INHALED flavours before, taking these into the body through the lungs.
The information regarding real risk is only found in crevices on the net. Big money to be made and real concerns are not getting much traction as of yet, alas.