My answer to What are the dangers of eLiquid?
Answer by Miles Dolphin:
The main danger of any e-liquid is in the mixing of it! A competent mixer will select the right ingredients and will combine them to make a safe e-liquid – it may taste foul, but it is difficult to make a dangerous one assuming the ingredients are all good.
Selecting your ingredients is fairly simple too, as long as you get pharma grade excipients, nicotine (below 10% strength is recommended), and the flavourings come from suppliers who supply to the vaping industry. There are two dangers here, getting over-strength nicotine, which at high levels is a poison, and getting flavourings which are not recommended for inhaling. The flavours which are not suggested contain things likewhich in high concentration can do severe damage to your lungs, but even in the concentrated e-cig flavouring form it is never strong enough to do so.
Any physician will tell you, regarding anything toxic, is that the poison is in the dose. In all commercial e-liquids (barring accidents) there is never enough of any bad ingredient to do you harm. Even drinking 30ml (which I strongly advise against) of e-liquid at 24mg/ml will probably only give you a headache and a nasty bout of vomiting, although if it were to be injected intravenously it would do serious harm.
A report (2014) says that e-liquid is as dangerous as washing-up liquid.
Shared to my blog