From the article, it seems it&#x27;s the flavourings that are added to e-cig liquid that seem to be causing the problem.<p>Presumably the effect would be the same if the same flavourings were added to &#x27;real&#x27; cigs, but, with the exception of menthol, that isn&#x27;t commonly done.<p>Why are flavourings so popular with e-cig? Does the liquid (glycerin?) have a foul taste that they are trying to mask?