I can be pretty bad at jumping on people reporting weird problems with vaping, and I do wonder why sometimes.
A bit of irony with it is that I had a whole raft of problems when I started vaping, I should be more sympathetic I would think.
Just relaying a few things that have happened to me with different juices and ingredients.
I cant vape PG all day, it affects me after 20-30mins vaping.
To get to the point of figuring out that it was PG that was the problem and to find a solution and an enjoyable vape I worked through everything that is involved in converting juice into vapour. Juice and its ingredients, wick and coil material, temperature and any other variable.
I can vape unflavoured vg/pg/nic for a short while and if I stop at the right time I might just feel a bit dry in the sinus's. Sometimes I feel like a flavour just for a change but I havnt really found anything that works well with just VG and DW so I mix up batches of flavours just for when I might feel like a flavour that work out to about 30pg/70vg.
What I have found is that there are some flavours that really speed up the reaction I have with pg and increase the symptoms. I can feel myself reacting within a very short time, sometimes within just a few puffs. The reaction can actually initially feel kinda "full" and good like the best part of a cigarette! right up until it starts feeling bad, and then it feels horrible
Ive also had one litre batch of VG that made me feel ill. I wasnt sure what was going on but my usual unflavoured brew made me feel ill. I thought I must have failed to sterilize everything properly so I started again from scratch and was careful to sterilize everything thoroughly. Cleaned and rewicked my atty and tried the new batch only to feel a bit ill. I noticed a slight difference in the taste compared to an older batch. I filled an atty with just the vg and another atty with some other vg. They tasted different and the bad tasting vg made me feel ill.
I dont know if the VG was out of code or if it hadnt been bottled hygienically or what was going on but I ditched it and found another supplier.
When I first started vaping and before I really started having a problem with PG I bought some pre made juice, a vanilla custard or something. It made me feel quite ill and I gave it to a work mate and told him my problem with it with the advice to just ditch it rather than vape it, he vaped it, he was too ill to come in to work the next night.
It was that experience that got me started into DIY, and then the final straw which sent me into DIY completely was developing a pg intolerance.
That turned out to be a longer post than I thought it was going to be.