While I think the OP is jumping to conclusions, I also think the other posters are too quick to dismiss his/her valid concerns. The truth is none of you are doctors and have no business "diagnosing" this guy's condition.
I tend to agree it is probably a coincidence or an allergy to PG, but it might not be. I will always be the first to say to go see a doctor if you are concerned. However, the only problem with seeing a doctor is most of them have NO CLUE about vaping. If you tell them you are vaping they will look at you like you have two heads (I know I have already ran it past my doctor).
Which brings me in agreement with the OP: we simply do not know the extent of how safe or unsafe vaping is. If doctors have no clue, then message board posters have less of a clue. I agree there needs to be some regulation of some sort, mainly because, I as a consumer, am worried about mom and pop shops not knowing WTH they are doing when it comes to mixing e-liquid. That's why I will recommend you only stick to "big vendors" like HALO who are known for strict quality controls and who ship out tons of e-liquid.
What do we know about vaping so far? We know that no one has ever died (to our knowledge) from vaping. Some people have went to the ER for problems, but most of the time it had nothing to do with vaping or was a result of an allergy from the e-liquid. These people fully recovered. (Keep in mind that anyone can have an allergy to almost anything. Some people can die from eating peanuts, but it doesn't mean peanuts are inherently unsafe for most people). I have heard of people having PG allergies and even some having to seek medical treatment from vaping due to this allergy. I have never heard of the allergy being bad enough that the patient died, however. Doesn't mean it hasn't happened, but I am sure it would have made the news if it had.
We also have two reports of lipoid pneumonia from e-cigs. One of them was in the U.S. and one was from the UK. However, medical experts have said it is impossible to get lipoid pneumonia from e-liquid because glycerin is not oil based (it is an alcohol). In the case of the U.S. woman (who survived) the doctors said in their report that it was a result of her e-liquid. I see two possibilities:
1) Vaping was a coincidence and the patient inhaled oils from some other source (you have to inhale oils to get lipoid pneumonia). The doctors knew that glycerin was an ingredient in the e-liquid (and said so in their report) and they said it was the cause of the pneumonia. So either these doctors are ignorant of glycerin not being an oil or they know something the rest of us don't.
2) If it was the e-liquid, it most certainly was very bad quality liquid or a DIY project gone bad.
If lipoid pneumonia were a real problem with vapers, we would have heard about more than two cases. Two cases is statistically insignificant. Millions of people vape now, and I am sure we would have heard about more than two cases if lipoid pneumonia were a real threat.
We know that PG and VG are both safe for human consumption and for use on the skin. Both have been studied for decades and were long ago deemed GRAS (generally recognized as safe). However, PG can be toxic at high levels, especially if taken intravenously. This can happen with benzodiazepine injections (Benzodiazepines include drugs like Xanax, Ativan, Valium, etc). The drugs use PG as a dilutant. These are sometimes given through an IV to calm people during surgery or to treat certain illnesses. There have been documented cases in the literature of the PG in these drugs causing death, usually through something called lactic acidosis. PG results in an increase in lactic acid. The body typically converts lactate to pyruvate and metabolizes pyruvate through the Krebs cycle. However, if there is too much for too long of a period, you can go into lactic acidosis, which can result in death. See this case report: Severe lactic acidosis after an iatrogenic p... [Pharmacotherapy. 2010] - PubMed - NCBI
So the obvious question is: Is it possible to get lactic acidosis from inhaling PG? If so, how much does it take? We don't know. However, if it were possible, I am sure we would have heard about it by now. All indications are that it would take an inhalation of much more PG than any human could reasonably vape in a short period. Some people do report joint pain after having started vaping, and this makes sense if you recognize that PG breaks down into lactic acid in the body. Lactic acid is known to cause joint stiffness or pain. The best way to avoid this is to vape a mostly VG juice. Say 70VG or even 100 VG.
And finally, in my area, the pulmonologist (lung specialist) has actually recommended people vape instead of smoke. My vape shop has a list of doctors on their wall who have told their patients to go there to buy a kit. I am assuming this pulmonologist (and the other general practitioners) have at least done a modicum of research into the issue. And I am sure they came to the conclusion that vaping, while maybe still new and not well researched, has to be safer than smoking.
I suspect there will be findings in the future that vaping might cause this issue or that issue in some people or that it isn't as safe as some proponents think. However, I never think any serious research will show it to be anywhere as dangerous as smoking cigs.
I tend to agree it is probably a coincidence or an allergy to PG, but it might not be. I will always be the first to say to go see a doctor if you are concerned. However, the only problem with seeing a doctor is most of them have NO CLUE about vaping. If you tell them you are vaping they will look at you like you have two heads (I know I have already ran it past my doctor).
Which brings me in agreement with the OP: we simply do not know the extent of how safe or unsafe vaping is. If doctors have no clue, then message board posters have less of a clue. I agree there needs to be some regulation of some sort, mainly because, I as a consumer, am worried about mom and pop shops not knowing WTH they are doing when it comes to mixing e-liquid. That's why I will recommend you only stick to "big vendors" like HALO who are known for strict quality controls and who ship out tons of e-liquid.
What do we know about vaping so far? We know that no one has ever died (to our knowledge) from vaping. Some people have went to the ER for problems, but most of the time it had nothing to do with vaping or was a result of an allergy from the e-liquid. These people fully recovered. (Keep in mind that anyone can have an allergy to almost anything. Some people can die from eating peanuts, but it doesn't mean peanuts are inherently unsafe for most people). I have heard of people having PG allergies and even some having to seek medical treatment from vaping due to this allergy. I have never heard of the allergy being bad enough that the patient died, however. Doesn't mean it hasn't happened, but I am sure it would have made the news if it had.
We also have two reports of lipoid pneumonia from e-cigs. One of them was in the U.S. and one was from the UK. However, medical experts have said it is impossible to get lipoid pneumonia from e-liquid because glycerin is not oil based (it is an alcohol). In the case of the U.S. woman (who survived) the doctors said in their report that it was a result of her e-liquid. I see two possibilities:
1) Vaping was a coincidence and the patient inhaled oils from some other source (you have to inhale oils to get lipoid pneumonia). The doctors knew that glycerin was an ingredient in the e-liquid (and said so in their report) and they said it was the cause of the pneumonia. So either these doctors are ignorant of glycerin not being an oil or they know something the rest of us don't.
2) If it was the e-liquid, it most certainly was very bad quality liquid or a DIY project gone bad.
If lipoid pneumonia were a real problem with vapers, we would have heard about more than two cases. Two cases is statistically insignificant. Millions of people vape now, and I am sure we would have heard about more than two cases if lipoid pneumonia were a real threat.
We know that PG and VG are both safe for human consumption and for use on the skin. Both have been studied for decades and were long ago deemed GRAS (generally recognized as safe). However, PG can be toxic at high levels, especially if taken intravenously. This can happen with benzodiazepine injections (Benzodiazepines include drugs like Xanax, Ativan, Valium, etc). The drugs use PG as a dilutant. These are sometimes given through an IV to calm people during surgery or to treat certain illnesses. There have been documented cases in the literature of the PG in these drugs causing death, usually through something called lactic acidosis. PG results in an increase in lactic acid. The body typically converts lactate to pyruvate and metabolizes pyruvate through the Krebs cycle. However, if there is too much for too long of a period, you can go into lactic acidosis, which can result in death. See this case report: Severe lactic acidosis after an iatrogenic p... [Pharmacotherapy. 2010] - PubMed - NCBI
So the obvious question is: Is it possible to get lactic acidosis from inhaling PG? If so, how much does it take? We don't know. However, if it were possible, I am sure we would have heard about it by now. All indications are that it would take an inhalation of much more PG than any human could reasonably vape in a short period. Some people do report joint pain after having started vaping, and this makes sense if you recognize that PG breaks down into lactic acid in the body. Lactic acid is known to cause joint stiffness or pain. The best way to avoid this is to vape a mostly VG juice. Say 70VG or even 100 VG.
And finally, in my area, the pulmonologist (lung specialist) has actually recommended people vape instead of smoke. My vape shop has a list of doctors on their wall who have told their patients to go there to buy a kit. I am assuming this pulmonologist (and the other general practitioners) have at least done a modicum of research into the issue. And I am sure they came to the conclusion that vaping, while maybe still new and not well researched, has to be safer than smoking.
I suspect there will be findings in the future that vaping might cause this issue or that issue in some people or that it isn't as safe as some proponents think. However, I never think any serious research will show it to be anywhere as dangerous as smoking cigs.
Please speak for yourself as some of us have been around and active on these forums almost since they first started. 
