Whenever I use a sub ohm build with 50/50 pg/vf I tend to get a lot of hot juice sparks. Some of them end up around the drip tip and make their way to my lip.
if your juice is manufactured appropriately it should be composed of food grade ingredients only.
the only real concern is nicotine overdose if you are smoking like 24 mg...but I mean you would have to drink more then a few sparks...
According to the Department of Pharmacology and Toxicolog at, Karl-Franzens University (Austria) who tested the potential lower limit of nicotine overdose (specifically due to the rise of nicotine liquid ie. vaping), a cautious estimate puts the lower limit at 500-1000 mg
In essence, you'd have to drink more then 20 mL of 24mg....which I am sure you don't.
If you have access to journals the article is called "How much nicotine kills a human? Tracing back the generally accepted lethal dose to dubious self-experiments in the nineteenth century" published by Bernd Mayer
To understand it in depth you will need a bit of understanding about toxicology, but the gist of it, as it applies to the toxicity of nicotine is understandable to most =).
Hope this helps increase your knowledge about your ejuice!